BACKGROUND: Invasive cervical cancer is highly preventable, yet it continues to occur, even among women who have access to cancer screening and treatment services. To reduce cervical cancer among such women, reasons for its occurrence must be better understood. We examined factors associated with the diagnosis of cervical cancer among women enrolled in health plans. METHODS: We identified all cases of invasive cervical cancer (n = 833) diagnosed from January 1, 1995, through December 31, 2000, among women who were long-term members of seven prepaid comprehensive health plans and reviewed each woman’s medical records for the 3 years prior to her cancer diagnosis. Women were classified into one of three categories based on Pap test histories 4-36 months before diagnosis: failure to screen with a Pap test, failure in detection by a Pap test, or failure in follow-up of an abnormal test result. RESULTS: The majority of cases (n = 464; 56%) were in women who had no Pap tests during the period 4-36 months prior to diagnosis. Of the remaining cases, 263 (32%) were attributed to Pap test detection failure and 106 (13%) to follow-up failure. Being older (odds ratio [OR] = 6.48, 95% confidence interval [CI] = 3.89 to 10.79) or living in an area of higher poverty (OR = 1.72, 95% CI = 1.11 to 2.67) or having a lower education level (OR= 1.52; 95% CI = 1.07 to 2.16) was associated with the likelihood of being assigned to the failure to screen category versus either of the other two categories. A total of 375 (81%) of the 464 patients who had not had Pap screening had had at least one outpatient visit 4-36 months prior to cancer diagnosis. The cancer diagnostic process was triggered by a routine screening examination in 44% of patients, whereas 53% of the patients presented with symptoms consistent with cervical cancer; the remaining 3% were identified fortuitously during the course of receiving noncervical care. CONCLUSIONS: To reduce the incidence of invasive cervical cancer among women with access to screening and treatment, Pap screening adherence should be increased. In addition, strategies to improve the accuracy of Pap screening could afford earlier detection of cervical cancer.