The toxic effects of metal ions on alveolar macrophages and alveolar type 2 cells were studied in-vitro. Alveolar macrophages and type 2 cells, obtained from male Sprague-Dawley-rats, were incubated with divalent copper (15158119) (Cu), zinc (7440666), pentavalent arsenic (17428410) (As), trivalent vanadium (22541771), or tetravalent selenium (22541555) (Se) ions. The effects on oxygen consumption and membrane integrity of alveolar macrophages and type 2 cells were determined. The effects of the ions on chemiluminescence in zymosan stimulated alveolar macrophages were also determined. The metal concentrations for reducing oxygen consumption to 50 percent of the control value (ED50) in type 2 cells were: Cu, 0.0002 molar (M); zinc, 0.0003M; As, greater than 0.001M; vanadium, greater than consumption in alveolar macrophages were: Cu, 0.00003M; zinc, than 0.001M. Cu and zinc ions severely damaged the membrane integrity of alveolar macrophages, while vanadium ions exhibited intermediate toxicity. Cu, zinc, and vanadium ions slightly damaged the membrane integrity of alveolar type 2 cells. As and Se had no effect on the membrane integrity of alveolar macrophages or type 2 cells. The ED50 for inhibition of zymosan stimulated chemiluminescence were: Cu, 0.0000012M; zinc, 0.0000092M; vanadium, some metal ions can have detrimental effects on lung tissue. Metals are less toxic to alveolar type 2 cells than to alveolar macrophages.