The duration of protection offered by Pap screening for cervical cancer was examined using data on 101 cases of invasive cervical cancer and 396 controls from a Maryland case-control study. Receipt of a Pap test up to 4 years ago afforded significant protection, compared to women screened 11 or more years ago, or never screened. Smoking, intercourse before age 19, and a history of sexually transmitted disease were significant risk factors for cervical cancer; barrier contraception use was protective. Variation in protection from Pap screening was examined by age, race, age at first intercourse, barrier contraception use, and source of last Pap test (obstetrician-gynecologist vs other provider type). Results showed older women, women with earlier age of first intercourse, and non-users of barrier contraception received slightly less protection from Pap tests, while women who received their last Pap test from an obstetrician-gynecologist received significantly more protection than women who did not. Issues of quality of screening and follow-up are discussed in regard to these results.