This paper presents the development, optimization and validation of a LC-MS/MS methodology to determine the antiparasitic veterinary drug toltrazuril and its two main metabolites, toltrazuril sulfoxide and toltrazuril sulfone, in environmental surface water, soil and animal manure. Using solid phase extraction and selective pressurized liquid extraction with integrated clean-up, the analytical method allows for the determination of these compounds down to 0.06-0.13 ng L(-1) in water, 0.01-0.03 ng g(-1)dw in soil and 0.22-0.51 ng g(-1) dw in manure. The deuterated analog of toltrazuril was used as internal standard, and ensured method accuracy in the range 96-123% for water and 77-110% for soil samples. The developed method can also be applied to simultaneously determine steroid hormones in the solid samples. The antiparasitic drug and its metabolites were found in manure and soil up to 114 and 335 pg g(-1) dw, respectively. Little is known regarding the environmental fate and effects of these compounds; consequently more research is urgently needed.