Semen specimens from 21 men with urethral infection with Chlamydia trachomatis were tested for the presence of the organism before and after cryopreservation for 3 weeks of storage at -196 degrees C. Five specimens were chlamydia-positive before preservation and four of them were still positive after storage when examined by enzyme immunoassay (Chlamydiazyme). When examined by cell culture, four proved chlamydia- positive before storage and two afterwards. The results indicate that testing for C. trachomatis has to be performed from the urethra of all donors of semen used for artificial insemination before the inoculation takes place.