In a life-span study with female Han:NMRI virgin mice (300 of a fat subline, 300 of a lean subline, and 300 controls), a total of 424 mice developed 673 ovarian tumors. Half of the mice in each group were fed ad libitum, and for the other half food was restricted. Most prevalent were tubular adenomas followed by granulosa and Sertoli cell tumors. Altogether, 42 neoplasms were classified as tubular adenocarcinomas, and 21, as luteomas . The general incidence of tumors increased sharply beyond the 18th month of age. Granulosa cell tumors arose relatively early, and tubular adenocarcinomas occurred very late in life. The occurrence of ovarian tumors depended mainly on life expectancy. All animals subjected to food restriction lived longer and developed more ovarian neoplasms than those fed ad libitum.