The incidence of adenocarcinoma of the cervix in the USA more than doubled between the early 1970s and the mid 1980s among women under 35 years of age. It was suggested that this increase was due to the introduction of oral contraceptives in the early 1960s. Adenocarcinoma of the cervix diagnosed in women born after 1935 was identified between 1977 and 1991 from the Los Angeles County Cancer Surveillance Program. Data from personal interviews of 195 cases and 386 controls (matched on age, race, and neighbourhood) were analysed. Information on medical, sexual, contraceptive, and reproductive history, previous cervical smears, and sexually transmitted diseases was collected. Compared with never use, ever use of oral contraceptives was associated with twice as great a risk of adenocarcinoma of the cervix (adjusted odds ratio 2.1, 95% CI 1.1-3.8). The highest risk was observed for oral contraceptive use for more than 12 years (4.4, 1.8-10.8). No additional increased risk was found for early age at start of oral contraceptive use, use before age 20 or before first pregnancy, time since first use, time since last use, or particular formulations, once total duration of use had been accounted for.