Erythrocyte glucose-6-phosphate dehydrogenase (G6PD) was characterized in blood samples of 94 male subjects in Sudan having deficient and non-deficient electrophoretic variants. They comprised 44 GdB, 17 GdA, 19 GdB-, 11 GdA- and 3 non-deficient (GdKhartoum) variants. Biochemical characteristics including enzyme activity, electrophoretic mobility, Km for glucose-6-phosphate (G6P) and nicotinamide adenine dinucleotide phosphate (NADP), heat stability and pH optimum of all the common and deficient variants were consistent with the reported characteristics of these variants. The Gdĸhartoum variant had 9% mobility in TEB buffer and 100% in phosphate buffer, 120% activity, Km of 130 ± 49 µm for G6P and 0.8 ± 0.2 µm for NADP, lowered thermostabil-ity and an optimum pH of 7.6. This variant was not inhibited by 15 mM maleic acid, 10 m Miodoacetate and dehydro-iso-androsterone. All other variants were inhibited by dehydro-iso-androsterone but uninhibited by maleic acid and iodoace