Crohn's disease (CD) has been occasionally reported to be associated with myelodysplastic syndromes (MDS) or acute myeloid leukaemia (AML). From October 1991 to June 1993, four AML patients with a previous history of CD but no history of MDS were referred to our institution. Three presented AML with a monoblastic proliferation (one AML4 and two AML5). Cytogenetic analysis revealed a normal karyotype in two patients, an inv(16) in another and a del(11)(q24-25) in the fourth. Interestingly, the three patients with AML4/AML5 had not received high doses of immunosuppressive agents, prior CD therapy ranging from 1 to 4 months sulfasalazine with additional azathioprine in one case.