Airborne metallic particulates are associated with fossil-fueled power plants, automobile exhausts, metal mining, and metallurgical smelters. Therefore, the possible toxic effects of metals on the lung are of environmental and occupational concern. In this investigation we determined the effects of in vitro exposure to metallic ions on the following parameters: oxygen consumption and membrane integrity of alveolar macrophages and type II cells, and chemiluminescence of zymosan-stimulated alveolar macrophages. Cu2+ and Zn2+ exhibited marked toxicity to isolated alveolar macrophages and type II cells, while V3+ exhibited intermediate toxicity. In contrast, short-term in vitro exposure to As5+ and Se4+ had little effect on alveolar macrophages and type II cells. Although the data suggest that exposure to certain metals may be harmful to the lung, the various pulmonary parameters tested in this investigation display differing susceptibility to metal exposure. That is, metals are less toxic to alveolar type II cells than to alveolar macrophages. Our data also indicate that chemiluminescence is the most sensitive assay for monitoring the viability of alveolar macrophages, while oxygen consumption is a sensitive assay for type II cells.