Following complete DNA characterisation patients with Hb H disease were assigned into two groups: deletional (alpha +/alpha o) and non deletional (HbCS/alpha o). Earlier studies have indicated that the group with (HbCS/alpha o) has more severe clinical problems. The serum malonyldialdehyde (MDA) levels, a secondary product of lipid peroxidation were within the normal range, though significantly higher levels of MDA were seen in the non-deletional type of Hb H disease when compared with the deletional type. Markedly low vitamin E levels were also seen in the former group. There were no significant differences in clinical severity may be attributed to an interplay of the accelerated destruction of damaged mature red blood cells secondary to the oxidative denaturation of Hb H and inclusion precipitation; higher levels of Hb H and more inclusion precipitation were seen in the group with (HbCS/alpha o). Low levels of vitamin E in the (HbCS/alpha o) group being due to its consumption in the neutralisation of free radicals formed with the oxidation of globin chains.