To better understand why smokers are more likely to develop cervical cancer than nonsmokers, we investigated laboratory and demographic differences between the two groups. Women between the ages of 18 and 49 who attended eleven community clinics in the San Francisco Bay Area were studied to investigate differences between smokers and nonsmokers. The 332 smokers and 365 nonsmokers were queried about smoking habits, sexual and reproductive history, and recent diet. Cervical mucus specimens were cultured for yeast, lactobacillus, and other microorganisms. Results showed that white Hispanic women were less likely to smoke than white non-Hispanic women. Smokers, when compared to nonsmokers, consumed larger quantities of coffee, soft drinks, liquor, and beer in the 24 h prior to the interview. Women who smoked were more likely than those who did not smoke to have had first sexual intercourse before age 16, had a greater number of lifetime sexual partners, and were more likely than nonsmokers to have been pregnant. After controlling for number of sexual partners, smokers reported a history of chlamydia, gonorrhea, and/or pelvic inflammatory disease more often than did nonsmokers, and cervical mucus of smokers was more likely than that from nonsmokers to contain greater than 8500 microorganisms/ml.