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

EXHIBIT 99

To our shareholders,

We are pleased to report record quarterly net income in the third quarter of $15,274,000, or $1.88 per diluted share, compared to $11,086,000, or $1.39 per diluted share, in third quarter 2004. Return on average equity was 18.30% in third quarter 2005 compared to 15.54% in third quarter 2004, return on average assets was 1.39% versus 1.10%, and efficiency ratio was 59.96% versus 66.02%.

Quarterly Results

Net interest income of $44,617,000 in third quarter 2005 was $7,063,000 more than third quarter 2004. The net interest margin of 4.60% increased 28 basis points over the same period last year. Compared to second quarter 2005, net interest margin increased 19 basis points. Third quarter 2005 average loans grew $277,855,000, or 11%, while quarterly average deposits grew $188,264,000, or 6%, over the same period last year. Improved credit quality also contributed to the earnings growth in third quarter 2005. With improving loan quality, the provision for loan loss of $1,375,000 was $1,012,000, or 42%, lower than third quarter 2004.

Noninterest income of $17,462,000 was $1,959,000, or 10%, lower than third quarter 2004. Third quarter 2005 noninterest income included a $1,811,000 loss on the sale of U.S. agency securities which were replaced with higher yielding securities. Further, in third quarter 2004, the Cut Bank branch was sold resulting in a gain of $1,690,000. Excluding the loss on securities in 2005 and Cut Bank gain in 2004, noninterest income increased 9% from third quarter 2004.

Noninterest expense of $37,142,000 was $418,000, or 1%, lower than the comparable quarter in 2004. In third quarter 2005, we recorded a $985,000 mortgage servicing impairment reversal compared to a $1,180,000 impairment for the third quarter of 2004. Without the effect of mortgage servicing impairment, noninterest expense would have been $1,747,000, or 5% higher than last year.

During first quarter 2005, we announced our strategic decision to exit Wal-Mart locations. Third quarter expenses of $55,000, in addition to $897,000 recognized year to date through second quarter, were recognized directly as a result of preparing to close these locations. In second quarter 2005, we discontinued operation of five of the nine Wal-Mart locations. The remaining four Wal-Mart locations are expected to be closed by January 2006.

On October 11, 2005, the Company paid a $.50 dividend per common share.

Year to Date

On a year to date basis, net income of $40,113,000, or $4.94 per diluted share, was $6,737,000, or 20.2%, higher than net income in the first three quarters of 2004 of $33,376,000, or $4.19 per diluted share. Return on average equity was 16.82% in the first three quarters of 2005 compared to 15.76% last year, return on average assets was 1.26% versus 1.13%, and efficiency ratio was 62.79% versus 64.18%.

When comparing the year to date performance of 2005 to 2004, there are some significant items that affect comparability. One such item is a decrease in the expense for provision for loan losses. Due to improving credit quality, the provision for loan losses in 2005 was $4,365,000 as compared to the 2004 provision expense of $7,346,000, a difference of $2,981,000. Also, in 2005 we recorded

impairment reversal income of $1,297,000 related to our mortgage servicing rights, as compared to 2004 when we recorded impairment expense of $104,000. Additional expenses related to the closure of Wal-Mart branches totaled $952,000 in the first three quarters of 2005.

We have made good progress towards improving the Company’s return on assets, and are seeing signs of progress towards improving the efficiency of the Company. With increased yields in our investment portfolio and loan growth, net interest margin of 4.47% has increased 11 basis points on a year to date basis over last year. Despite signs of progress, however, efficient implementation of our community banking philosophy remains a high priority.

Thanks to our talented team of employees, officers and advisory directors for the achievement of another record in quarterly earnings. Thank you.

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

Financial Highlights
Three Months ended September 30

(unaudited)	2005		2004		% Change
(in thousands except per share data)
OPERATING RESULTS
Net income	$	15,274	$	11,086		37.8	%
Diluted earnings per share		1.88		1.39		35.1	%
Dividends per share		0.48		0.40		20	%
PERIOD END BALANCES
Assets		4,457,739		4,063,162		9.7	%
Loans		2,982,325		2,674,963		11.5	%
Investment Securities		887,912		843,415		5.3	%
Deposits		3,477,115		3,236,518		7.4	%
Common Stockholders’ Equity		342,166		302,299		13.2	%
Common Shares Outstanding		8,097		7,980		1.5	%
QUARTERLY AVERAGES
Assets		4,369,721		3,998,892		9.3	%
Loans		2,929,238		2,651,383		10.5	%
Investment Securities		894,369		799,916		11.8	%
Deposits		3,390,945		3,202,681		5.9	%
Common Stockholders’ Equity		331,174		283,837		16.7	%
Common Shares Outstanding		7,981		7,887		1.2	%

Third Quarter 2005

Third Quarter 2005

Condensed Consolidated Statements of Income

	Three Months Ended				Nine Months Ended
	September 30				September 30
(unaudited)	2005		2004		2005		2004
(in thousands, except per share data)
Total interest income	$	61,423	$	48,143	$	168,934	$	141,756
Total interest expense		16,806		10,589		44,112		30,666
Net interest income		44,617		37,554		124,822		111,090
Provision for loan losses		1,375		2,387		4,365		7,346
Net interest income after provision for loan losses		43,242		35,167		120,457		103,744
Noninterest income		17,462		19,421		52,251		53,172
Noninterest expense		37,142		37,560		111,181		105,431
Income before taxes		23,562		17,028		61,527		51,485
Income taxes		8,288		5,942		21,414		18,109
Net income	$	15,274	$	11,086	$	40,113	$	33,376
COMMON SHARE DATA:
Diluted EPS		1.88		1.39		4.94		4.19
Dividends		0.48		0.40		1.38		1.14
Book value						42.26		37.88
Tangible book value						37.64		33.20
Appraised value						*		55.50

*Currently not available, $65.50 as of June 30, 2005

Selected Ratios

	Three Months Ended						Nine Months Ended
	September 30						September 30
(unaudited)	2005			2004			2005			2004
PERFORMANCE
Return on avg common equity		18.30	%		15.54	%		16.82	%		15.76	%
Return on avg common equity excl. market adj of securities		18.19	%		15.02	%		16.59	%		15.63	%
Return on avg assets		1.39	%		1.10	%		1.26	%		1.13	%
Net interest margin, FTE		4.60	%		4.32	%		4.47	%		4.36	%
Efficiency ratio		59.96	%		66.02	%		62.79	%		64.18	%
CREDIT QUALITY (Period End)
Annualized provision for loan losses to average loans								0.21	%		0.38	%
Annualized net charge offs to average loans								0.15	%		0.20	%
Allowance for loan losses to loans								1.45	%		1.58	%
Allowance for loan losses to non-accruing loans								258.01	%		189.12	%
CAPITAL ADEQUACY & LIQUIDITY
Leverage capital ratio								7.71	%		7.34	%
Avg loans to avg deposits								85.55	%		82.61	%

It’s our home too

Condensed Consolidated Balance Sheet

	September 30
(unaudited)	2005		2004
(In thousands)
ASSETS
Cash and due from banks	$	203,983	$	233,071
Federal funds sold		105,150		56,415
Interest bearing deposits		14,874		6,816
Investment securities		887,912		843,415
Loans		2,982,325		2,674,963
Less: allowance for loan losses		43,213		42,396
Net loans		2,939,112		2,632,567
Premises & equipment, net		120,086		120,015
Accrued interest receivable		26,931		22,015
Goodwill and core deposit intangibles		38,847		39,878
Mortgage servicing rights		20,558		16,871
Bank owned life insurance		61,975		59,961
Other assets		38,311		32,138
Total Assets	$	4,457,739	$	4,063,162
LIABILITIES AND STOCKHOLDERS’ EQUITY
Deposits	$	3,477,115	$	3,236,518
Securities sold under repurchase agreements		495,269		401,078
Other liabilities		38,499		31,443
Other borrowed funds		6,435		8,051
Long — term debt		57,017		42,535
Subordinated debenture		41,238		41,238
Total Liabilities		4,115,573		3,760,863
Common stockholders’ equity		342,166		302,299
Total Liabilities and Stockholders’ Equity	$	4,457,739	$	4,063,162