In two men aged 65 and 40 years with abdominal pain, the diagnosis ‘acute acalculous cholecystitis’ (AAC) could be reached only after exploratory laparotomy. The first patient was initially admitted to the coronary-care department because of known atherosclerotic vascular disease; he died a few days after the operation due to sepsis. The second patient recovered satisfactorily after admission to intensive care because of haemodynamic instability. AAC is an illness with a non-specific clinical presentation and incomplete radiologic imaging. AAC is more frequently seen in outpatients than in acutely ill inpatients, especially in older male patients who have atherosclerotic vascular disease. Diagnostic and therapeutic delay leads to gangrene, empyema and perforation, resulting in a high mortality. To improve the outcome, a high and early index of suspicion is needed. Hepatobiliary scintigraphy should be included in the diagnostic pathway.