Background: Nationally representative surveys of chlamydia and gonorrhea are an important measure of disease burden and progress of screening programs.

Objective: To measure chlamydia and gonorrhea prevalence in the United States.

Design: Analysis of sexual history information and urine specimens collected in the National Health and Nutrition Examination Survey (NHANES), 1999-2002.

Setting: U.S. civilian noninstitutionalized population as sampled by NHANES, 1999-2002.

Participants: 6632 NHANES respondents.

Measurements: Urine specimens were tested for chlamydia and gonorrhea. Results were weighted to represent the U.S. civilian, noninstitutionalized population between 14 and 39 years of age.

Results: Prevalence of gonorrheal infection was 0.24% (95% CI, 0.16% to 0.38%). Prevalence of gonorrheal infection was higher among non-Hispanic black persons (1.2% [CI, 0.7% to 1.9%]) than among non-Hispanic white persons (0.07% [CI, 0.02% to 0.24%]). Among those with gonorrheal infection, 46% also had chlamydial infection. Prevalence of chlamydial infection was 2.2% (CI, 1.8% to 2.8%) and was similar between males (2.0% [CI, 1.6% to 2.5%]) and females (2.5% [CI, 1.8% to 3.4%]). Among females, the highest prevalence was in those age 14 to 19 years, whereas among males, it was highest in those age 14 to 29 years. Prevalence was higher among non-Hispanic black persons (6.4% [CI, 5.4% to 7.5%]) than non-Hispanic white persons (1.5% [CI, 1.0% to 2.4%]). Among females with a history of gonorrhea or chlamydia in the previous 12 months, chlamydia prevalence was 16.7% (CI, 5.5% to 50.7%).

Limitations: The specificity of urine-based assays for chlamydia and gonorrhea is limited, and the possible misclassification of sexual experience status may have affected the accuracy of some estimates.

Conclusions: The findings support current recommendations to screen sexually active females age 25 years or younger for chlamydia, to retest infected females for chlamydial infection, and to co-treat individuals with gonorrhea for chlamydia.