The involvement of reactive oxygen species in the toxicity of cadmium (Cd) has been proposed. We have, therefore, examined the effects of this cation on the production of superoxide anion and nitric oxide and DNA single strand breaks in J774A.1 macrophage cells in culture as well as the effects on lactate dehydrogenase (LDH) leakage and cell viability. Following a 48-h incubation, over 2-fold increases in superoxide anion and nitric oxide (NO) production were observed at a Cd concentration of approximately 0.60 microM, while a 50% decrease in viability was observed at this concentration. LDH leakage paralleled the superoxide anion and nitric oxide production. Concentration-dependent increases in DNA single strand breaks (SSB) were observed after incubation with Cd with a maximum increase occurring at a concentration of approximately 0.40 microM. The results indicate that Cd is toxic to the J774A.1 cell line, and support the hypothesis that the toxicity may be due at least in part to an oxidative stress induced by the production of reactive oxygen species following exposure to this cation.