Irish men and women are at equal risk of developing Crohn's disease. Age at diagnosis (12--mean 30.5-75 yr) and duration of symptoms before diagnosis (1--mean 35.7-444 months) are similar to those for Crohn's disease in other countries. The proportion of patients with macroscopic involvement of the large bowel at diagnosis (68%) is increasing and this is probably a true increase. At the same time the incidence of perianal disease is probably decreasing. Extraintestinal manifestations probably occur more frequently than previously recognized. Crohn's disease and psoriasis, which occurred in 7% of the patients, are probably associated disorders.