Early morning first-void urine collected from 279 sexually active Swedish male recruits (mean age 19.5 years) was tested by two commercial enzyme immunoassay (EIA) kits, MicroTrak and IDEIA III, and by MicroTrak direct fluorescence assay (DFA), to detect Chlamydia trachomatis antigens. A result was assumed to be true-positive when any of the two non-culture tests were positive for the same specimen. In one case where only DFA was positive, confirmatory chlamydial testing was performed by isolating the organism from a urethral swab. On these premises, the number of true-positive men was 26 (9.3% of all men studied). The sensitivity, specificity, positive predictive value and negative predictive value for MicroTrak EIA were 85%, 98%, 85%, and 98%, respectively. IDEIA III was less sensitive than MicroTrak EIA (42% vs 85%). In conclusion, the diagnosis of asymptomatic chlamydial infections in men can be established with reasonable accuracy by the detection of Chlamydia antigens in urine samples using MicroTrak EIA.