The incidence of intestinal adenocarcinoma in Crohn's ileal disease is reported in the literature to be higher than in the normal population. The authors report two cases of adenocarcinoma observed during the course of Crohn's ileitis and, by comparing these findings with earlier published data, highlight their characteristics. Two patients, a 53-year-old woman and a 62-year-old man, are reported as suffering from Crohn's ileitis. The woman underwent resection of the right colon with ileo-transversostomy due to stenosis twenty years earlier, whereas diagnosis in the male patient dates back to an appendicectomy 11 years earlier. Surgery, which was performed in both due to subocclusion which failed to respond to steroid therapy, showed the typical alterations of Crohn's disease. An adenocarcinoma was also found in both patients in the stenotic zone with highly dysplasic foci. The man presented a monoclonal gammopathy of an IgA-type with light lambda chains and Bence-Jones' proteinuria. Both patients are living and enjoy apparently good health respectively 2 and 6 years after surgery. The authors emphasize that the association between Crohn's ileal disease and intestinal adenocarcinoma cannot be considered casual. In the literature the relative risk is reported to be between 6 and 320 times higher, with approximately 1 out of 350 patients suffering from both diseases contemporaneously. In the series reported earlier, 2 cases of carcinoma were diagnosed in 38 Crohn's patients studied over a period of 12 years out of a total population of 114000 inhabitants, with a frequency of carcinoma of 5.13% compared to 0.3% reported in the literature. The incidence of Crohn's disease was 2.84/100000 per year.(ABSTRACT TRUNCATED AT 250 WORDS)