The effects of combined exposure to lead (74339921) (Pb) and high ambient temperature on tissue distribution of Pb, body weight gain, and thermoregulation were examined. Groups of 10 male rats each were subjected to combinations of 23 or 33 degrees C temperatures and 1.0 percent lead-acetate (301042) in the diet. One group remained untreated as a control. Thermoregulatory response was examined for each group except controls on days 7, 14, and 28. During the sixth week of exposure, all animals were heated from a resting to a lethal temperature to determine the total heating time. Immediately after lethal temperature was attained, the adrenal glands and samples of brain, liver, spleen, heart, skeletal muscle, and bone marrow were obtained for subsequent digestion and Pb analysis. Blood also was obtained and analyzed for Pb content. Lead ingestion at an environmental temperature of 33 degrees C resulted in reduced food intake and a decrease in body weight. The two agents appeared to exert a synergistic effect. Heating time to lethal temperature was significantly increased in rats maintained at 33 degrees C, with or without Pb treatment. The lead content of the adrenal glands, spleen, and bone marrow from Pb fed rats maintained at 33 degrees C was significantly higher than that of animals maintained at 23 degrees C. The liver, blood, skeletal muscle, and brain Pb contents of rats kept at 33 degrees C were similar to values obtained for rats receiving Pb at 23 degrees C. The authors conclude that the differences in Pb distribution found in the tissues of Pb fed rats at 23 and 33 degrees C suggest that concomitant high temperature and Pb exposure have a significant effect on the uptake and retention of Pb in specific tissues.