Neutrophil function in 40 workers occupationally exposed to carbamate and organophophate insecticides were examined and compared to those of non-exposed individuals. Phagocytosis and intracellular killing of Candida albicans and Candida pseudotropicalis by neutrophils were studied. Two species of Candida were used since in individuals with myeloperoxidase deficiency neutrophils are unable to kill Candida albicans, while Candida pseudotropicalis can be effectively lysed. Phagocytosis of both antigens was normal in all the workers studied. On the other hand, there was a considerable reduction in the ability of neutrophils from exposed workers to kill Candida albicans whereas Candida pseudotropicalis was effectively lysed. This finding indicates some interference with the myeloperoxidase activity in the exposed population. The levels of cholinesterase activity in all workers were normal. These results demonstrate that exposure to carbamates and organophophates insecticides may lead to changes in neutrophil function even in workers presenting no impairment in the cholinesterase activity.