Different heme proteins such as hemoglobin (Hb) have been proposed to be major prooxidants in raw and cooked meats. Despite the fact that the content of Hb in meat is considerable, little attention has been devoted to Hb in comparison to myoglobin. To understand the mechanisms and differentiate between the prooxidant and antioxidant potential of oxyhemoglobin (OxyHb) and methemoglobin (MetHb), their prooxidant activity, protein solubility, radical scavenging capacity, iron content and the relative weight of non-chelatable iron on lipid oxidation were determined as a function of thermal treatments. The ability of native OxyHb and MetHb to promote lipid oxidation was similar and higher than those Hb heated at 68 and 90 C but not different from that at 45 C.However, the prooxidant activity of MetHb heated at 68 and 90 C were similar whereas OxyHb heated at 68 C was higher than that heated at 90 C. The decreased prooxidant activity of heat denatured Hb was associated with a decrease in the solubility of heme iron while free iron showed little impact on the lipid oxidation onset.