We report three patients aged 75-80 years observed in the Emergency Room with severe anaemia (requiring transfusion) due to a large abdominal wall haematoma while receiving standard prophylaxis against venous thromboembolism (40 mg/day enoxaparin for 6 days on average). All of them concomitantly received 100 mg/day aspirin because of previous ischaemic heart disease and presented similar clinical features: sudden onset of abdominal pain during a severe cough episode due to bronchial infection. A giant haematoma in the rectus abdominis muscle was recognized (by computed tomography) in every case. The cough has been related with this complication in some reports but its association with antiplatelet drugs and low molecular weight heparin could increase the risks in older patients. Sudden abdominal pain must alert the clinician to the rectus muscle sheath haematoma in order to avoid the risks of an exploratory laparotomy.