We examined a total of 1014 patients over 18 years of age; 252 with urethritis and 762 with chronic prostatitis syndrome. the mean age of patients with urethritis was 32.7 and with prostatitis syndrome 37.6 years. Clinical symptoms of urethritis were present from a few days to several months. in patients with chronic prostatitis syndrome, symptoms were present for at least 3 months. Chlamydia trachomatis alone was confirmed in 26 (10%) and in combination with Ureaplasma urealyticum in 6 (2%) patients with urethritis. in 171 (68%) patients with urethritis neither C. trachomatis nor U. urealyticum or Mycoplasma hominis were found. C. trachomatis alone was confirmed in 70 (9%), and in combination with other microorganisms in 7 (1%) patients with chronic prostatitis syndrome. in Croatia, the frequency of chronic chlamydial prostatitis has not significantly changed in the last 10 years, while the frequency of infections among adolescents decreased. the recommended regimen for acute chlamydial urethritis in Croatia is azithromycin 1.0 g as a single dose, and a total dose of 4-4.5 g azithromycin for chronic chlamydial prostatitis.