Spontaneous gallbladder perforation is a rare complication of acute cholecystitis. The mechanism for the development of this complication is not clear, although a vascular anomaly and ischemia of the gallbladder appear to be important predisposing factors. It is rarely diagnosed preoperatively, and the delay in making the definitive diagnosis usually accounts for the increased incidences of morbidity and mortality associated with this complication. We experienced the unusual case of a 64-year-old male pa tient who presented with a 1-h history of generalized, especially right upper quadrant, abdominal pain. He had no history of traumatic, atherosclerotic, cardiovascular, metabolic disease. Abdominal ultrasono graphy demonstrated generalized free intraperitoneal fluid, especially in right lower quadrant, and was otherwise unremarkable. On palpation, his abdomen was rigid, and a provisional diagnosis of perforated peptic ulcer was made. The patient underwent a cholecystectomy. Gross examination of the gallbladder showed a pinhole perforation (1.2x1.0 mm2) in the body, but no gallstones. Microscopic examination of the wall revealed some neutrophile and lymphocyte infiltration and Widal test was negative. The patient had an uneventful recovery.