The metabolism, excretory rates, and excretory patterns of carbon 14 ( 14 C) radiolabeled estradiol (E 2 ) and testosterone (T) were studied in female budgerigars (Melopsittacus undulatus) and orange-winged Amazon parrots (Amazona amazonica). Radiolabeled E 2 and T were injected intramuscularly into six budgerigars and two orange-winged Amazon parrots. Serial fecal/urine samples were collected for 168 h post-radiolabel injection. Peak radiolabeled E 2 excretion was observed at 4 h post-injection, and by 24 h, 93.3 Β± 6.3 and 65.9% (range, 59.1-72.7%) of the injected radiolabel was recovered in the fecal/urine matter of budgerigars and orange-winged Amazon parrots, respectively. Similarly, peak radiolabeled T excretion was observed at 4 h postinjection with 92.7 Β± 3.6 and 66.2% (range, 57.5-75.2%) of the injected radiolabel recovered in the fecal/urine matter by 24 h in the budgerigars and orange-winged Amazon parrots, respectively. High-performance liquid chromatography (HPLC) analysis of the fecal/urine material revealed that both parrot species excreted >80% of the radiolabel in the form of complex steroid conjugates. Immunoreactive E 2 and T metabolites were detected using estrone (E 1 ) and C-21/C-19 conjugate enzyme immunoassays, respectively. Hydrolysis of the E 2 metabolites and HPLC analysis of the ether extracts revealed that E 2 and E 1 were the major steroid moieties. Hydrolysis of the T metabolites and HPLC analysis of the ether extracts revealed two and three major unconjugated peaks for the budgerigars and the orange-winged Amazon parrots, respectively. Zoo Biol 18:247-260, 1999.