1. The metabolism of two pesticides, 3,4',5-tribromosalicylanilide (TBS) and 4',5-dibromosalicylanilide (DBS) has been studied after oral administration to rats. 2. Approximately 65% of the dose of TBS is absorbed, and then excreted as glucuronide and sulphate conjugates of two hydroxylated metabolites. One of these has been identified as 4'-hydroxy-3,5-dibromosalicylanilide, while evidence suggests that the other metabolite is 5-hydroxy-3,4'-dibromosalicylanilide. 3. In contrast, only 11% of the dose of DBS is absorbed; it is then excreted mainly as glucuronide and sulphate conjugates of the parent molecule.