One adolescent and two young adults had ulcerative colitis and cerebral thrombosis. All survived with neurologic deficit. These patients had no other predisposing factor for cerebrovascular disease. Systemic arterial and venous thromboembolic complications occur often in ulcerative colitis, but stroke is uncommon. Abnormalities in the early stages of clotting may be responsible, and the risk of thromboembolic phenomena in young patients seems to increase with exacerbations of this form of chronic inflammatory bowel disease, and possibly with regional enteritis as well.