Prior to the early 1970's, benign liver neoplasms were among the rarest of tumors. The seemingly rapid increase, especially in young females ingesting oral contraceptives, as well as the catastrophic presentation of many of the tumors resulting from liver rupture and hemoperitoneum, stimulated studies by several investigators. In the Liver Tumor Registry at the University of Louisville, we have examined the histologic material, and finalized the data on 227 tumors, the majority in young women. With few exceptions, they had used oral contraceptives or were either pregnant or immediately post-partum and presumably in a hyperestrogenic state. There have been 82 hepatocellular adenomas (HCA), 105 cases of focal nodular hyperplasia (FNH), and 31 hepatocellular carcinomas. The hepatocellular carcinomas occurred in non-cirrhotic livers, and 14 of the 31 cases were of a distinct, but rare type, polygonal cell carcinoma with lamellar fibrosis. While it seems reasonable to believe steroids play a role in adenomas and in FNH it is less certain that they produce hepatocellular carcinomas since malignant liver tumors are not uncommon in this age group without the use of oral contraceptives. With an estimated 50 million women either currently using or who have used oral contraceptives the risk must be very slight.