A 77-year-old woman was under follow-up for a cyst of 8cm in diameter in S8 of the liver with multiple small cysts all found incidentally by ultrasound in August 1997. She was admitted to our hospital complaining of fever and right hypochondralgia in November 1997. This was diagnosed as infection of the cyst in S8. The infected cyst was aspirated under sonographic guidance and drainage started. A catheter cystography performed after remission showed a peripheral bile duct communicating with the infected cyst. An operation was indicated since no further contraction of the cyst was obtained. The hepatic segment which included the infected cyst was excised by partial hepatectomy in December 1997. No recurrence has been encountered for the first four months postoperatively. Since an infected liver cyst communicating with the biliary tract is considered to have a possibility of recurrence, an operation such as hepatectomy is indicated early in the course of treatment.