Objective: To determine prevalence of Chlamydia trachomatis (C. trachomatis) in aymptomatic and symptomatic men with genitourinary infection. Sample included 300 male participants (age ranged from 20-69) who approached CNIPH Laboratory for testing on C. trachomatis infection in period from October 2003 to March 2004. Based on clinical data patients were divided in 4 categories: I. Symptomatic patients (nonspecific urethritis), N=109 II. Asymptomatic participants (test was a part of extended periodical general medical examination), N=90 III. Asymptomatic participants (came because their partner has some symptoms in genital or urethral area), N=83 IV. Asymptomatic participants (came due to infertility problems), N=18. Urethral swabs were tested by enzyme immunoassay - EIA for detection of chlamydial antigen (MicroTrak II Chlamydia EIA-Trinity Biotech). Positive results were confirmed by direct fluorescent-antibody test - DFA (MicroTrak II Chlamydia trachomatis Direct Specimen Test). Overall prevalence of C. trachomatis was 8%. Average age of positive patients was 30.2 years. The prevalence of symptomatic C. trachomatis infections was 18.3%, while the prevalence of asymptomatic C. trachomatis infections was 2.1% (in the group II the prevalence was 1/90, in the group III - 2/83, and in the group IV - 1/18). Since reporting of C. trachomatis positive cases is known to be underestimated, it is valuable to continue the study in order to obtain more objective data about prevalence of symptomatic and asymptomatic C. trachomatis infections in men in Croatia.