A 50 year old man presented with peripheral oedema, abdominal distension and a pulmonary opacity on CXR. He subsequently perforated his sigmoid colon as a complication of diverticulitis with pericolic abscess. After colectomy his postoperative period was marked by severe hypokalaemia, metabolic alkalosis, hyperglycaemia and recurrent chest infections. Paraneoplastic Cushing's syndrome was diagnosed after finding elevated serum cortisol and ACTH levels. CT-guided biopsy of the lung lesion revealed small-cell carcinoma. Bone scan disclosed collapse of numerous thoracic vertebrae possibly due to osteoporosis or oncogenic osteomalacia. Treatment with steroid-synthesis blockers was commenced but the patient died before tumour-directed therapy could be started. Ectopic ACTH syndrome and oncogenic osteomalacia are discussed.peer-reviewe