Oxytetracycline hydrochloride (OTC) was delivered to adult parakeets by aerosolization using a DeVilbiss model 65 ultrasonic nebulizer. Trachea, lung, and plasma concentrations were ascertained at 1, 2, 4, 6, and 8 hours postaerosolization (PA). An average of 284 ml of a solution containing 2 mg OTC/ml was aerosolized over a 1-hour period into a 0.0596 M3 chamber containing 10 parakeets. The trachea and lung concentrations were more than 10 micrograms/g at 1 and 2 hours PA, had decreased to approximately 3 micrograms/g by 4 hours PA, and were below 2 micrograms/g by 8 hours. The plasma concentration never exceeded 2.6 micrograms/ml and was at 1.6 micrograms/ml by 8 hours. This study demonstrates that it is possible to achieve therapeutic concentrations of OTC by aerosolization in lung and trachea, but treatment may need to be repeated every 4-6 hours. Since the plasma concentration never reached high levels, aerosolization under the conditions of this study is not an effective way to treat systemic infections outside the respiratory tract.