The estrogen, androgen, and progestogen excretion rates of farm animals in the US have been estimated to be 49, 4.4, and 270 t/yr. Land application of manure thus has the potential for steroid hormone leakage or runoff into the aquatic environment. Steroid hormones can cause endocrine disruption in humans and wildlife. Consequently, it is important to determine the fate of steroid hormones to enable predictions of their long-term effects in the environment. The objectives of this study were thus to determine the impact of direct and indirect photolysis by UVA light and (bio)degradation by manure-borne bacteria on the fate of steroid hormones. Samples containing 17beta-estradiol, testosterone, or progesterone were irradiated with UVA-light. Experiments were conducted in 10 mM phosphate buffer (pH 5.5) in the absence and presence of photosensitizers (i.e. 10 mg/L KNO3, 5 mg/L humic acid (HA), or a mixture of KNO3 and HA). The impact of a pure E. coli strain and manures from cattle, turkeys, and swine on the degradation of testosterone was studied in aerobic batch experiments by adding testosterone to the E. coli strain or the manures in flasks that were subsequently put on a shaker. Samples were taken out periodically and analyzed for parent-compound and potential degradation products using HPLC-DAD and mass spectrometry. Photolysis of 17beta-estradiol, testosterone, and progesterone was observed. Interestingly, 17beta-estradiol was only photolyzed in the presence of HA. Testosterone and progesterone were both directly photolyzed; however, increased photolysis was observed for testosterone in the presence of HA. The half-lives for the photolytic reactions ranged from 3 to 6 hours. Ongoing work involves the manure related studies and characterization of (photo)degradation products formed in these experiments. This study indicates that photolysis of hormones might be an important removal mechanism in aqueous environments and that humic acid can influence the photodegradation potential.