The effect of recombinant interleukin 3 (IL-3) on the function of murine resident peritoneal macrophages was investigated. IL-3 enhanced the phagocytosis of Candida pseudotropicalis and Candida albicans and enhanced killing of the former. The enhanced killing is inhibited by scavengers of oxygen radicals, suggesting that IL-3 primes macrophages for enhanced oxidative metabolism in response to Candida.