We report a case with abdominal complications of clofazimine treatment which included blackish discolouration of the lymph nodes, omentum and perito- neum. A 44-year-old female with lepromatous leprosy and a history of adverse reaction to clofazimine 2 years previously, presented with rectosigmoid junction adenocarcinoma. Laparotomy revealed an inoperable tumour with pigmentation of the bowel, serosa and peritoneum. A second operation had o be performed for transverse loop colostomy and a mesenteric lymph node biopsy sent for frozen section showed typical clofazimine crystals. Despite widespread use for many years in the treatment of leprosy, this drug is not known to be carcinogenic and this case provides no evidence for an association or link between its use and the patient’s cancer. Apart from its use in leprosy, clofazimine may be used in the treatment of disseminated Mycobacterium avium-intracellulare infection, Buruli ulcer due to M. ulcerans and occasionally in other mycobacterial infections. An awareness of the rare side-effect described above may help in the clinical assessment and management of such cases, including the avoidance of unnecessary laparotomy.