Daniel & Gage (1966) reported that the amount of 14C-diquat excreted in rat bile during the 24 h following oral doses of 1.2 - 64 mg/kg body weight represented 1.1 - 4.8% of the dose. Small amounts were detected in the urine, but about 70% of the diquat was present in the faeces. In other studies (FAO/WHO, 1978), the rate of diquat metabolism in the rat was considerably lower than previously reported by Daniel & Gage (1966). The biliary, urinary, and faecal excretion of 14C-labelled bipyridylium herbicides was studied by Hughes et al. (1973) in the rat, guinea-pig, and rabbit.