To evaluate anti-colitic efficacy, eight cotton-top tamarins (CTTs) with histologically confirmed persistent active colitis were given the anti-inflammatory agent SC-41930 (10 mg/kg BW by gavage BID) for eight weeks. Colonic endoscopy and biopsy observations, CBCs and clinical chemistries, and stool consistency were evaluated pre-, mid-, and posttreatment. Colitic activity was graded histologically from A1 (mild) to A5 (severe); results varied among the seven animals that completed the study: five improved, one worsened, and one was unchanged. Serum enzyme levels were significantly reduced with treatment. Stool condition remained puddly throughout treatment and body weights did not vary from pretreatment levels. However, SC-41930 produced histological evidence (reduced numbers of polymorphonuclear cells) of anti-colitic efficacy over an eight-week treatment period in CTTs with persistent active colitis. These results support the use of the CTT colitis model to evaluate efficacy of therapeutic agents and provide useful predictive information to aid in the medical management of human IBD.