First Interstate BancSystem (FIBK) 8-K Results of Operations and Financial Condition

EXHIBIT 99

To our shareholders,

We are pleased to announce First Interstate BancSystem has achieved record earnings for the 17th consecutive year. The company earned $54,715,000 in 2005, a 20% increase over the prior year’s earnings of $45,421,000. Diluted earnings per share were also a record $6.71, up $1.03 from 2004. Return on average common equity in 2005 was 16.79%, compared to 15.75% in 2004. Our efficiency ratio improved to 62.65%, down from 64.68% in 2004.

Annual

Net interest income of $170,308,000 increased $19,889,000 over 2004. Loans grew by $294,845,000, or 11%, while deposits grew $225,909,000, or 7%. The net interest margin of 4.48% was 14 basis points higher than 2004. Our growth and improved net interest margin are particularly noteworthy in light of the flattening of the yield curve during 2005. Typically, a flattening yield curve constrains a bank’s ability to maintain its net interest margin. Further, lower levels of non-performing loans, net charge-offs and internally classified loans allowed us to reduce the provision for loan losses $2,886,000 compared to 2004.

Total noninterest income for 2005 was $354,000 lower than 2004. The reduction of noninterest income was mainly the result of $3,677,000 of losses recognized on the sale of U.S. agency securities. The securities were replaced with higher yielding securities. Further contributing to the decline in noninterest income was a gain of $1,690,000 recognized in 2004 due to the sale of a branch office for which there was no similar gain in 2005.

Total noninterest expense of $150,726,000 was $7,746,000 higher than 2004. During first quarter 2005, we announced our strategic decision to exit Wal-Mart locations. Total expenses of $1,088,000 were recognized in 2005 as a result of preparing to close these locations. Five Wal-Mart locations were merged into other First Interstate branches during 2005 with three additional Wal-Mart branches merged in January 2006 and one Wal-Mart branch sold in January 2006. In addition, salary and benefits expense of $80,029,000 was $6,057,000 higher than 2004. This increase reflects the effect of 2005’s results on incentive compensation and profit sharing for employees and officers as well as annual increases to salaries due to normal inflationary adjustments. Mortgage servicing impairment reversals of $2,187,000 in 2005 compared to $263,000 in the prior year reduced the effect of these expense increases in 2005.

Fourth Quarter

Earnings of $14,602,000 in the fourth quarter were the highest fourth quarter results in company history. Earnings were $2,557,000, or 21%, higher than fourth quarter 2004. Diluted earnings per common share of $1.77 were up $.28 from last year. Return on average common equity of 16.70% was up 100 basis points from the prior comparable quarter. The efficiency ratio was 62.25%, a nearly 4 percentage point improvement over 2004.

Net interest income was $6,157,000 higher in the fourth quarter of 2005. Average loans grew $308,793,000, or 12%, while average deposits grew $210,931,000, or 6% compared to fourth quarter 2004. Net interest margin of 4.49% increased 19 basis points.

Noninterest income of $18,039,000 was $567,000 higher than fourth quarter 2004. Residential real estate loan fee revenue increased $211,000 and bank income from debit and credit card activity increased $665,000. Fourth quarter 2005 contained losses on the sale of U.S. agency securities of $737,000 compared to losses of $35,000 in fourth quarter 2004. The securities were replaced with higher yielding securities.

Noninterest expenses increased $1,996,000 or, 5%, over fourth quarter 2004. Salary and benefits accounted for $1,992,000 of this increase. In addition, advertising increased $130,000 and First Interstate foundation contributions, driven by higher corporate earnings, increased $187,000 over fourth quarter 2004. The mortgage servicing rights impairment reversal, which was $523,000 higher than last year, dampened somewhat the effect of these increases during the last quarter of 2005.

On January 10th, 2006, the company paid a $.50 dividend per common share. The Company recently announced that the dividend payable in April 2006 will increase to $.58 per share.

Despite a challenging interest rate environment, 2005 proved to be remarkable in the history of First Interstate BancSystem. Achieving earnings of over $50 million was truly a milestone. Additionally, we continued to grow and to improve the efficiency of our operations. These results confirm the strength of our values and our community banking strategy.

We are grateful for the extraordinary performance of our employees, officers and directors and the opportunities provided us. Thank you and hearty congratulations!

Lyle R. Knight	Terrill R. Moore
President	Executive Vice President
Chief Executive Officer	Chief Financial Officer

Financial Highlights
Three Months ended December 31

(unaudited)	2005		2004		% Change
OPERATING RESULTS
Net income	$	14,602	$	12,045		21.2	%
Diluted earnings per share		1.77		1.49		18.7	%
Dividends per share		0.50		0.42		19.0	%
PERIOD END BALANCES
Assets		4,562,313		4,217,293		8.2	%
Loans		3,034,354		2,739,509		10.8	%
Investment Securities		1,019,901		867,315		17.6	%
Deposits		3,547,590		3,321,681		6.8	%
Common Stockholders’ Equity		349,847		308,326		13.5	%
Common Shares Outstanding		8,099		7,980		1.5	%
QUARTERLY AVERAGES
Assets		4,555,990		4,186,552		8.8	%
Loans		2,998,797		2,690,004		11.5	%
Investment Securities		943,169		854,795		10.3	%
Deposits		3,520,455		3,309,524		6.4	%
Common Stockholders’ Equity		346,881		305,179		13.7	%
Common Shares Outstanding		8,090		7,978		1.4	%

Fourth Quarter 2005

Fourth Quarter 2005

Condensed Consolidated Statements of Income

	Three Months Ended				Twelve Months Ended
	December 31				December 31
(unaudited)	2005		2004		2005		2004
(in thousands, except per share data)
Total interest income	$	64,923	$	51,084	$	233,857	$	192,840
Total interest expense		19,437		11,755		63,549		42,421
Net interest income		45,486		39,329		170,308		150,419
Provision for loan losses		1,482		1,387		5,847		8,733
Net interest income after provision for loan losses		44,004		37,942		164,461		141,686
Noninterest income		18,039		17,472		70,290		70,644
Noninterest expense		39,545		37,549		150,726		142,980
Income before taxes		22,498		17,865		84,025		69,350
Income taxes		7,896		5,820		29,310		23,929
Net income	$	14,602	$	12,045	$	54,715	$	45,421
COMMON SHARE DATA:
Diluted EPS		1.77		1.49		6.71		5.68
Dividends		0.50		0.42		1.88		1.56
Book value						43.20		38.68
Tangible book value						38.58		33.99
Appraised value						*		63.00

* Currently not available, $68.00 as of September 30, 2005

Selected Ratios

	Three Months Ended						Twelve Months Ended
	December 31						December 31
(unaudited)	2005			2004			2005			2004
PERFORMANCE
Return on avg common equity		16.70	%		15.70	%		16.79	%		15.75	%
Return on avg common equity excl. market adj of securities		16.48	%		15.67	%		16.56	%		15.64	%
Return on avg assets		1.27	%		1.14	%		1.26	%		1.14	%
Net interest margin, FTE		4.49	%		4.30	%		4.48	%		4.34	%
Efficiency ratio		62.25	%		66.10	%		62.65	%		64.68	%
CREDIT QUALITY (Period End)
Provision for loan losses to average loans								0.20	%		0.33	%
Net charge offs to average loans								0.19	%		0.21	%
Allowance for loan losses to loans								1.40	%		1.54	%
Allowance for loan losses to non-accruing loans								247.84	%		239.85	%
CAPITAL ADEQUACY & LIQUIDITY
Leverage capital ratio								7.91	%		7.49	%
Avg loans to avg deposits								85.46	%		82.27	%

It’s our home too

Condensed Consolidated Balance Sheet

	December 31
(unaudited)	2005		2004
(In thousands)
ASSETS
Cash and due from banks	$	207,877	$	235,251
Federal funds sold		27,607		37,590
Interest bearing deposits		5,493		83,067
Investment securities		1,019,901		867,315
Loans		3,034,354		2,739,509
Less: allowance for loan losses		42,450		42,141
Net loans		2,991,904		2,697,368
Premises & equipment, net		120,438		121,928
Accrued interest receivable		26,104		20,569
Goodwill and core deposit intangibles		38,594		39,607
Mortgage servicing rights		22,116		17,624
Company owned life insurance		62,547		60,645
Other assets		39,732		36,329
Total Assets	$	4,562,313	$	4,217,293
LIABILITIES AND STOCKHOLDERS’ EQUITY
Deposits	$	3,547,590	$	3,321,681
Federal funds purchased		1,500		0
Securities sold under repurchase agreements		518,718		449,699
Other liabilities		41,271		26,428
Other borrowed funds		7,495		7,995
Long — term debt		54,654		61,926
Subordinated debenture		41,238		41,238
Total Liabilities		4,212,466		3,908,967
Common stockholders’ equity		349,847		308,326
Total Liabilities and Stockholders’ Equity	$	4,562,313	$	4,217,293