This study investigated the interacting effects of acute lead exposure and different diets on antibody and T-cell-mediated immunity in Japanese quail (Coturnix coturnix). Nine quail (nine week old males) were assigned randomly to each group in a factorial experiment with four treatments and two diets. The treatments were 1) a positive control group fed 20 micrograms/g corticosterone, 2) a negative control group given no lead or corticosterone, 3) a low-lead group, and 4) a high-lead group. The low and high lead groups received 100 and 400 micrograms/ml lead as lead acetate in drinking water for 7 d. The two diets were poultry feed and ground corn. Control quail fed corn lost 13-14% of initial body mass, but lead-dosed quail fed corn lost 23-24%. All quail fed poultry feed gained body mass. On the corn diet, three high-lead and one low-lead quail died of lead poisoning. Corn increased the percentage of heterophils in white blood cells (P = 0.0018) and decreased lymphocytes (P = 0.019) and monocytes (P = 0.0073). There was marginal evidence that lead increased the heterophil/lymphocyte ratio in corn-fed quail (P = 0.064). Corn decreased the T-cell-mediated response to an intradermal injection of phytohemagglutinin (P = 0.0001). Corticosterone suppressed this response more than lead. In corn-fed quail, lead suppressed the primary total antibody response to immunization with chukar partridge (Alectoris graeca) erythrocytes (P < 0.05). Lead reduced the secondary total antibody and IgG responses in the low lead, corn group (P < 0.05). Lead suppressed antibody-mediated immunity only at dosages that also caused clinical lead poisoning.