Three separate experiments were conducted to investigate the effects of heat treatment on meat heme and nonheme iron bioavailability in anemic rats. Male weanling Sprague-Drawley rats were first made anemic, then subsequently fed with experimental diets. In the first experiment, dietary iron sources were raw or autoclaved meat mixed with ferrous sulfate to give the ratios of iron from meat and ferrous sulfate equal to 100:0, 75:25, 50:50, 25:75, and 0:100 respectively. For the second experiment, the dietary iron sources were raw or autoclaved meat mixed with bovine hemoglobin (HB) to give dietary iron ratios as described for experiment 1. For experiment 3, dietary iron sources were boiled meat and baked meat. Known amounts of the experimental diets were fed the anemic rats for a 10-day repletion period. Body weight, hemoglobin concentration and hematocrit were determined before and after the repletion period. The animals were then sacrificed and the liver iron content was measured, as was the iron content of the feces from the last 7 days on test of each rat. In vitro digestion was done to determine the amount of soluble iron in the diets. Heat treatment increased the bioavailability of iron from hemoglobin from 23% to 30%. The effect of cooking on the bioavailability of iron from meat and ferrous sulfate were negligible. The efficiencies of conversion were 35, 37, 36 and 37 for raw meat, autoclaved meat, boiled meat and baked meat, respectively. Ferrous sulfate gave the highest bioavailability in anemic rats (65%). As the dietary proportion of iron from ferrous sulfate increased, the dietary iron bioavailability increased proportionally. Iron bioavailability decreased as the proportion of dietary iron from hemoglobin (HB) increased. Meat did not increase the bioavailability of iron from either ferrous sulfate or hemoglobin. Heat treatment decreased the heme iron content in the diets but did not affect the amount of soluble iron. Soluble iron content increased as the dietary proportion of iron from ferrous sulfate or hemoglobin (HB) increased. There was no correlation between the iron. bioavailability in rat and the soluble iron content determined by in vitro digestion.