Southwest Bancorp is buying a Pico Rivera bank.

Southwest Bancorp, based in San Diego County, said it has agreed to acquire Pacific Western National Bank in Pico Rivera in an exchange of stock. Southwest Bancorp has about $300 million in assets, while Pacific Western’s assets total about $46 million. Southwest will pay the equivalent of 1 1/2-times book value for Pacific Western’s shares, but the overall cost of the deal was not disclosed. The acquisition requires regulatory and shareholder approvals.