This is a report of a 13(1/2) year old girl with bilateral benign cystic ovarian teratomas (BCOT). The clinical presentation was with an abdominal mass and an abdominal X-ray film confirmed the mass which contained teeth. Previous abdominal X-ray at 3 and 10 years of age had not shown any abnormality. The clinical features and the radiological findings indicated that the BCOT had enlarged and matured during the period of follow-up.