This paper evaluates the differences between HCA (hepatocellular adenoma) and FNH (focal nodular hyperplasia) and the association of HCA and FNH with OC (oral contraceptives). FNH occurs at least twice as frequent in females as in males. A study conducted by the author revealed that only 20% of patients with FNH had symptoms and signs related to their neoplasms; in the rest, FNH was accidentally discovered during surgery for diseases of the gallbladder or at necropsy. The highly characteristic gross appearance of FNH is discribed in detail. The etiologic relationship between FNH and OC was cited in the light of frequent findings of FNH in infants and children, and of suggestions by other authors that FNH could be a direct result on OC therapy or that contraceptive steroids or conjugated estrogens accelerate the growth of FNH, a very slow growing neoplasm. Simple excision is the treatment of choice for FNH; in some cases, hepatic artery ligation is indicated. In the case of HCA, statistics show that the incidence of HCA has been increasing since 1960. Majority of patients with HCA have normal tests of hepatic function. Radiographic studies and hepatic scans may reveal HCA, but the best diagnostic method so far is angiography. Although gross appearance of HCA is variable, the features are clearly distinguishable from that of FNH. Other topics discussed include the occasional occurence of nodular regenerative hyperplasia in patients on OC or anabolic steroids (AS), and malignant liver tumors in patients using OC or AS. Further research should be done to clarify the etiologic relationship between androgenic-anabolic steroids and hepatocellular tumors and tumorlike lesions.