One hundred thirty-six unselected patients with Crohn's disease (43 men, 93 women) were studied for the possibility of psoriasis and questioned regarding their family history, as were 136 controls, matched for age and sex. Psoriasis was present in 13 of the 136 patients with Crohn's disease (9.6%), compared with three of 136 controls (2.2%) (p less than 0.02). Age at onset and anatomical site of Crohn's disease did not influence the result, and there was no difference between the sexes. Fourteen (three with psoriasis) of the 136 Crohn's patients (10%) had a family history of psoriasis in first-degree relatives compared with four of 136 controls (2.9%) (p less than 0.02). Psoriasis is more common in patients with Crohn's disease and their first-degree relatives than in controls, suggesting the possibility of a genetic link. Psoriasis should be included among the extraintestinal manifestations of the condition.