Principal Financial (PFG) 10-Q 2010 Q2 Quarterly report

Exhibit 32.2

Certification Pursuant to Section 1350 of Chapter 63
of Title 18 of the United States Code

I, Terrance J. Lillis, Senior Vice President and Chief Financial Officer of Principal Financial Group, Inc., certify that (i) the Form 10-Q for the quarter ended June 30, 2010, fully complies with the requirements of Section 13(a) of the Securities Exchange Act of 1934 and (ii) the information contained in the Form 10-Q for the quarter ended June 30, 2010, fairly presents, in all material respects, the financial condition and results of operations of Principal Financial Group, Inc.

/s/ Terrance J. Lillis

Terrance J. Lillis

Senior Vice President and Chief Financial Officer

Date: August 4, 2010