Southwest reported $49.7 million in nonperforming assets at the end of 2012, an increase of $8.1 million, or 20 percent from $41.6 million from the end of the third quarter.
The increase was from placing $12.5 million in loans in nonaccrual status and because of an increase in loans more than 90 days past due.
The company's nonperforming assets make up about 3.73 percent of its portfolio loans and other real estate.
Southwest Bancorp. is the parent company of Stillwater National Bank and Trust Co. and Bank of Kansas.
The company had $2.1 billion in assets at the end of 2012 and a market capitalization of about $240 million.
Shares in Southwest closed at $12.34, up 0.57 percent, or 7 cents, Wednesday on the Nasdaq.