It was the aim of the presented work to test Enrofloxacin under field conditions of compulsory prophylaxis and treatment of psittacosis, as JUNG (1993) had already demonstrated the effectiveness of this antibiotic against Chlamydia psittaci. During official quarantine 22 groups comprising 2536 birds were treated with Baytril. With suitable feed like steamed maize and a dose of 500 mg/kg Enrofloxacin the mean blood values ranged from 0.9 to 4.1 micrograms/ml within the different species. Application via drinking water can only be advised as an alternative in sick birds with reduced food intake. Duration of excretion (limit was the minimal inhibitory dose of Enrofloxacin with Chlamydia psittaci, 0.125 micrograms/ml was depending on the uptake of Enrofloxacin and correlated with serum levels. With mean serum levels of 1.0 micrograms/ml the minimal inhibitory dose for Chlamydia psittaci was attained in all birds after 14 days. The tissue concentrations measured in Patagonian conures surpassed serum levels several-fold, with the exception of brain tissue. Out of 22 quarantine groups only two were naturally infected with Chlamydia. One group of 196 Senegal parrots could only be cured from chlamydial infection after substituting their normal mixed feed with medicated maize containing 1000 mg/kg Enrofloxacin. In 50 per cent of the Salmonella infected groups Salmonella could again be grown from faecal samples after the end of treatment. For the treatment of psittacosis mean blood levels of 0.5 micrograms/ml are imperative and duration of treatment should not be below 14 days. Satisfactory hygienic conditions provided Baytril is a valuable therapeutic drug against psittacosis.