Ninety-seven asymptomatic 16-21-year-old sexually active adolescent males were evaluated for gonorrhea and chlamydia by culture, chlamydia enzyme immunoassay, and an analysis of a random urine sample for pyuria using centrifuged urine and urine cytometer. The incidence of gonorrhea was 5.3% and chlamydia by culture 12.3%. Immunoassay was superior in sensitivity and specificity (75% and 99%, respectively) to centrifuged urine (sensitivity 58%, specificity 92%) or urine cytometer (58% and 91%) in identifying asymptomatic chlamydia urethritis. Chlamydia enzyme immunoassay is an acceptable, more rapid, and less expensive alternative to culture. The absence of pyuria in asymptomatic males cannot be assumed to indicate the absence of a sexually transmitted disease.