Objective:To study the long‐term ovarian neoplastic consequences of resection of a dermoid cyst.Methods:The study population comprised 99 patients who were operated on for an ovarian dermoid cyst. Follow‐up information was obtained for 91 women for a mean period of 5.06 ± 2.46 years.Results:Of the 99 women, 18 had bilateral dermoid cysts. Multiple dermoid cysts in a single ovary were found in nine of the women with bilateral cysts and in one of the remaining patients. Two patients developed malignant germ cell tumors, and three developed a recurrent dermoid cyst in an ovary from which a dermoid cyst had previously been extracted. Bilateral or multiple ovarian dermoid cysts were present at the initial operation in four (80%) of these patients.Conclusions:Women with bilateral or multiple dermoid cysts may include a subgroup of patients with a greater tendency to develop future ovarian germ cell neoplasms.(Obstet Gynecol 1994;83:605‐8)