Lead is an element of risk for the environment and human health and has harmful effects that may exceed those of other inorganic toxicants. The immune system is one of the targets of lead. Its immunomodulatory actions depend on the level of exposure, and it has been demonstrated that environmental amounts of the metal alter immune function. Very little information is available regarding the effect of the metal on different aspects of the immune system of lower vertebrates, in particular of amphibians. The aim of this study was to investigate the effect of sublethal lead (as acetate) on the function of polymorphonuclear cells of Bufo arenarum. The results revealed that phagocytic and lytic functions of the adherent blood cells collected from sublethal lead-injected toads and incubated with suspensions of Candida pseudotropicalis were affected negatively. The decrease of the phagocytic activity was correlated with increased blood lead levels (P < 0.0001). Additional information referred to the total and differential leukocyte counts was presented; the only difference found was in the number of blast-like cells that resulted augmented in the samples of lead-injected toads. It was concluded that the evaluation of these parameters might be a reliable tool for the biological monitoring of the immune status of amphibians.