When poultry litter is landspread, steroidal hormones present in the litter may reach environmental waters, where they may have undesirable biological effects. In a laboratory study, we determined the mineralization of [414C]-labeled 17-estradiol, estrone, and testosterone in breeder and broiler litter at three different water potentials (-56, -24, and -12 MPa) and three different temperatures (25, 35, and 45C). Mineralization was similar in both litters and increased with increasing moisture and decreasing temperature. After 23 weeks at -24 MPa, an average of 27, 11, and <2% of the radiolabeled testosterone applied to breeder litter was mineralized to 14CO2 at 25, 35, and 45C, respectively. In contrast, mineralization of the radiolabeled estradiol and estrone was <2% after 25 weeks at both water potentials, except after 17 weeks at 25C and -12 MPa, where up to 5.9% of the estradiol and 7.8% of the estrone was mineralized. The limited mineralization suggests that the litters may still be potential sources of hormones to environmental waters.