Glucose-6-phosphate dehydrogenase (G6PD) enzyme from cases known to be completely or mildly deficient were analyzed. The enzymes were purified from blood samples by utilizing DEAE-52 cellulose pH 7.0 column chromatography and ammonium sulphate precipitation. Biochemical and electrophoretic properties of G6PD were studied in these partially purified enzymes. In this study we report three new variants from Cukurova, named Adana, Samandağ, and Balcali. Variant I (G6PD Adana) had a high Km for G6P (210 microM) and NADP (13 microM). Utilization of 2d-G6P was 38%. It had a slow electrophoretic mobility, a biphasic pH optimum curve, and abnormal heat stability. Variant II (G6PD Samandağ) had a low Km for G6P (25 microM) and a high Km for NADP (18 microM). The rate of utilization of 2d-G6P was normal. G6PD Samandağ deviated from the normal enzyme by its biphasic pH optimum curve and its slow electrophoretic mobility. Variant III (G6PD-Balcali) had a normal Km G6P, NADP and rate of utilization of 2d-G6P. However, it showed a biphasic pH optimum curve and slow electrophoretic mobility.