To evaluate the relationship between selfreported correct and consistent condom use and chlamydial and gonococcal infection. Design: Cross-sectional study. Setting: An urban adolescent health care clinic. Patients: A total of 509 adolescent girls tested for Chlamydia trachomatis and Neisseria gonorrhoeae infection by urine nucleic acid amplification tests. Main Outcome Measure: Effect of condom use on infection rates of chlamydia and gonorrhea. Consistent condom use was defined as using condoms for every act of vaginal sex and correct use as consistent use without any of the following: beginning sex without a condom, taking it off before finishing sex, flipping it over, condom breakage, or condom slippage. Results: A total of 95% of the participants were African American, with a mean age of 16.6 years. Chlamydia prevalence was 21% (105/509) and gonorrhea prevalence was 7% (36/509). Condom errors were reported by 316 (71% ) of 442 participants who had reported using a condom at least once in the previous 3 months. Consistent use was reported by 176 patients (35% ); however, both correct and consistent use was reported by only 80 patients (16% ). After adjusting for confounders, correct and consistent use was protective for chlamydia (odds ratio, 0.4; 95% confidence interval, 0.2- 1.0) and highly protective for gonorrhea (odds ratio, 0.1; 95% confidence interval, 0- 0.7). Conclusion: Our findings indicate that assessing both correctness and consistency of use is important for evaluation of condom effectiveness. To evaluate the relationship between selfreported correct and consistent condom use and chlamydial and gonococcal infection. Design: Cross-sectional study. Settings: An urban adolescent health care clinic. Patients: A total of 509 adolescent girls tested for Chlamydia trachomatis and Neisseria gonorrhoeae infection by urine nucleic acid amplification tests. Main Outcome Measure: Effect of condom use on infection rates of chlamydia and gonorrhea. Consistent condom use was defined as using condoms for every act of vaginal sex and correct use as consistent use without any of the following: beginning sex without a condom, taking it off before finishing sex, flipping it over, condom breakage, or condom slippage. Results: A total of 95% of the participants were African American, with a mean age of 16.6 years. Chlamydia prevalence was 21% ( 105/509) and gonorrhea prevalence was 7% (36/509). Condom errors were reported by 316 (71%) of 442 participants who had reported using a condom at least on However, both correct and consistent use was reported by only 80 patients (16%). After adjusting for confounders, correct and consistent use was protective for chlamydia (odds ratio, 0.4; 95% confidence interval, 0.2-1.0) and highly protective for gonorrhea (odds ratio, 0.1; 95% confidence interval, 0-0.7). Conclusion: Our findings indicate that assessing both correctness and consistency of use is important for evaluation of condom effectiveness.