Among 569 patients with Crohn's disease, 24% had a history of at least one extraintestinal manifestation and 36% had a history of perianal disease before randomization. Multiple extraintestinal manifestations occurred in the same patient more frequently than would be expected by chance. Seventy-six percent of patients with ileocolitis had perianal disease, extraintestinal manifestations, or both. This was significantly greater than the 58% incidence in patients with disease confined to the small bowel. Perianal complications alone were significantly more common in patients with colitis or ileocolitis than in those with disease of only the small bowel. This was true also of internal fistulization. There was a significant positive association between perianal disease and the presence of extraintestinal features. Perianal abscess appeared to respond to sulfasalazine and anal fissure to prednisone or azathioprine. These results require confirmation in larger series of patients.