We describe the spontaneous rupture of a simple hepatic cyst. A 62-year-old woman was admitted for right upper quadrant pain of sudden onset. The patient denied a history of abdominal trauma. Computed tomography of the abdomen showed a 13-cm-diameter solitary hepatic cyst in the right lobe. Part of the cyst surface was irregular, and the internal echo was heterogeneous. Retained fluid was detected under the liver capsule. Ten days after admission, computed tomography revealed that the volume of fluid retained under the liver capsule had decreased but that the hepatic cyst had enlarged again. The patient was referred to our hospital for further evaluation and treatment. Physical examination revealed mild right upper quadrant pain, but no signs or symptoms of peritonitis or abnormalities of the chest or heart. Percutaneous puncture was performed with a needle and an 8-French pigtail catheter under ultrasonographic guidance. Brown serous fluid was aspirated. After the removal of approximately 1,000 mL of fluid, contrast medium was injected to check for communications between the cyst and the biliary tree and to document the absence of leakage into the peritoneal cavity. After complete aspiration of the cyst fluid, 200 mg of minocycline hydrochloride dissolved in 10 mL of saline was injected into the cyst, and the catheter was flushed with 10 mL of saline (total volume of saline, 20 mL). The catheter was then clamped for 30 minutes. After percutaneous aspiration, the patient's symptoms resolved. Minocycline hydrochloride was injected daily for 7 days, and the catheter was removed. There has been no evidence of recurrence after 2 years.