To assess the prevalence, demographics, and transmission patterns of genital chlamydia infection, we screened 3,078 patients, and compared identified cases (N = 511) to gonorrhea cases (N = 291) diagnosed in the same setting. Chlamydia cases were younger and more likely to be White than their gonorrhea counterparts. Chlamydia cases were distributed diffusely; geographic overlap between the two diseases was only about 40 percent. Gonococcal coinfection was noted in less than 10 percent of patients with chlamydia. Nearly half of men with chlamydia and four-fifths of women were asymptomatic and most cases were identified through screening or contact tracing. Populations at high risk for chlamydia are seemingly different from those for gonorrhea. Differences may be due to control interventions (active for gonorrhea, passive for chlamydia). Chlamydia case reporting and control initiatives are recommended.