The incidence of adenocarcinoma of the cervix increased steadily in young women in the United States between the early 1970s and the mid-1980s. Despite this increase, little is known about the etiology of this cancer, although a role for risk factors for both squamous cell carcinoma of the cervix and endometrial adenocarcinoma has been suggested. Incident cases of adenocarcinoma of the cervix diagnosed in women born after 1935 (ages 42 to 56 at diagnosis) were identified from the Los Angeles (California) County Cancer Surveillance Program (LACCSP). Data from personal interviews with 195 cases and 386 controls (matched on age, race, and neighborhood) were analyzed. Compared with women in the highest categories of education and income, women in the lowest categories had a 2.5 and 3.1-fold elevated risk of adenocarcinoma of the cervix. Number of sexual partners, especially before age 20, was strongly predictive of risk (odds ratio = 5.6, 95 percent confidence interval = 1.4-22.0 for 10 or more compared with no partners before age 20). Smoking was not associated significantly with risk. Weight gain and long-term use of oral contraceptives increased risk, while long-term diaphragm use was protective. This study suggests that both sexual and hormonal factors are important etiologic factors for adenocarcinoma of the cervix.