Despite an extensive literature examining the relationship between Crohn's disease and psychiatric illness, there is only one published report of mania in a patient with Crohn's disease. The authors describe seven patients, six men and one woman, with both bipolar disorder and Crohn's disease. The age at onset of Crohn's disease was highly correlated with the age at onset of affective disorder (r = .89, p = .016) and mania (r = .79, p = .06). Four patients received prednisone therapy for Crohn's disease from 3 to 52 weeks before their first manic episode. The authors discuss the relationship of the two illnesses, including possible common provoking factors, the possible role of steroids, and the genetics of the disorders.