The irradiated Mc Coy cell cultures method modified by Darougar et al. has been used to investigate the frequency of Chlamydiae in non-specific genital tract disease, in Reiter's disease and in patients suffering from conjonctivits associated with non-specific urethritis. Isolates were obtained from 104 men of the 660 suffering from acute urethritis, and from 18 men of the 67 suffering from conjonctivitis associated with urethritis. Fourteen female sexual contacts of these men were tested: Chlamydiae was isolated from 9. Seven patients suffering from acute Reiter's disease were tested: Chlamydiae was isolated from 4. These patients were tested by complement fixation and titers of 1/8 or more were only obtained in the 4 isolated positive cases, the three other cases remaining negative. Isolates of Chlamydiae were obtained from 10 women of the 67 women suffering from exocervicitis. No isolate was obtained, from 27 control patients.