The association of oral contraceptive use with liver cancer was examined in a study of 76 deaths from primary liver cancer, 22 deaths from cancer of the intrahepatic bile ducts, and 629 controls among women aged 25 to 49 years. The subjects in the study are from the 1986 National Mortality Followback Survey, which included a questionnaire sent or administered to the next-of-kin of almost 20,000 deceased individuals in the United States. Information on a number of lifestyle factors was collected, including questions on oral contraceptive use. Increased risks of primary liver cancer were found for ever-users (odds ratio [OR] = 1.6, 95 percent confidence interval [CI] = 0.9-2.6), and for long-term (greater than or equal to 10 years) users (OR = 2.0, CI = 0.8-4.8) of oral contraceptives. When the analysis was restricted to subjects whose spouse or parent was the respondent, more pronounced risks were seen for ever-users (OR = 2.7, CI = 1.4-5.3) and long-term users (OR = 4.8, CI = 1.7-14.0). No clear excess risk was found for cancer of the intrahepatic bile ducts. This study, the largest to date, adds to the number of investigations demonstrating an increased risk of primary liver cancer with use, particularly long-term use, of oral contraceptives.