1 The antipyrine half-life, metabolic clearance rate and the apparent volume of distribution were measured in six subjects handling malathion. These results were compared with six appropriate controls.2 Occupational exposure of malathion in subjects reduced the antipyrine half-life from 9.18 ± 2.16 h in controls to 4.73 ± 1.65 h.3 It is concluded that malathion exposure increases the rate of antipyrine elimination, possibly by inducing the hepatic microsomal enzymes.