AbstractThe excretion of the coccidiostats sulphaquinoxaline and decoquinate has been studied in caged broilers on diets containing 100 and 30 mg kg−1of the drugs respectively. Sulphaquinoxaline reached a maximum excretion of 54 mg kg−1(based on dried excreta) in 18 days and decoquinate a level of 37 mg kg−1after 14 days. When the drugs were withdrawn from the feed the excreta concentration decreased to less than 2 mg kg−1in 3 days. Storage of contaminated excreta at 23°C for 9 days showed contrasting effects; the sulphaquinoxaline content decreased from 56 to 35 mg kg−1whereas the decoquinate concentration increased from 37 to 41 mg kg−1. Both coccidiostats appeared relatively stable when samples of excreta were dried in layers 1 cm thick in an o