Two hundred and two patients with Crohn's disease have been examined during the year 1984 to assess the frequency of perianal disease. One hundred and ten have had evidence of perianal complications (54%). In 30% of patients with perianal disease, the anal manifestations preceded any evidence of intestinal disease. Perianal disease was associated with pain in only 39%. Operations for perianal disease rarely achieved healing and were frequently associated with complications. Attempts to lay open a fistula-in-ano caused healing in only one of 12 cases and 6 developed incontinence. A high proportion of patients with Crohn's ulcers and strictures required proctectomy (87%). Proctectomy was performed in 27 patients with perianal disease of whom only 8 (30%) had primary healing of the proctectomy wound compared with complete healing in all 9 patients having a proctectomy without perianal disease (p less than 0.01). These results imply that patients with perianal Crohn's disease should be treated conservatively and that proctectomy, particularly in patients with rectal strictures, is associated with very high incidence of persistent perineal sinus.