From 1961 to 1989, 67 patients underwent various surgical procedures for psoas abscess. Retrospective analysis was undertaken in an effort to determine optimal surgical therapy. Forty patients were cured with one operation. Twenty-one patients required two operations, four patients required three operations, and two patients required more than three operations. The reason for failure of treatment was failure to resect the diseased bowel or to drain the psoas abscess adequately. A technique to recognize and treat the abscess definitively will be illustrated. The most common etiologies were Crohn's disease in 49 patients, postoperative sepsis in eight patients, and complications of renal disease in four patients. The length of hospital stay ranged from 5 to 392 days (mean, 26 days). There were two deaths. Failure to recognize and treat psoas abscess results in considerable morbidity.