During a one-year period, 101 parakeets and parrots were submitted for laboratory examination. The birds were sick, dead, or from premises where morbidity had been observed. Tissue specimens from these birds were tested for the presence of Chlamydiapsittaci by two methods. A tissue culture system using McCoy cells treated with 5-iodo-2-deoxyuridine was found to be more sensitive than intraperitoneal inoculation of mice for isolation of the chlamydiae. Chlamydiae were recovered from 21 (34%) of 61 parakeets and 16 (40%) of 40 parrots tested. This high rate of infection persists despite the availability of effective chemotherapeutic regimens for control of chlamydial infection in psittacines. The origins of some of the infected birds were traced to aviaries where subsequent treatment with chlortetracycline was successful in eradication of the chlamydial infection. Other infected birds had been imported recently and could be traced back to quarantine centers where (by law) the birds received chemoprophylaxis for chlamydial infection. Our results suggest that this program is an administrative failure.