Glucose-6-phosphate deydrogenase (G6PD, EC 1.1.1.49) has been detected in bacteria, protozoa, mammals and higher animals and also distributed in all the cell types of multicellular organisms. G6PD is the first and key regulatory enzyme of the pentose phosphate metabolic pathway. Ribose-5-phosphate that is required for nucleic acid synthesis and NADPH, a compound is used as coenzyme in various biosynthetic reactions, are produced in the end of pentose phosphate pathway. G6PD activity has been investigated in different reagions of Turkey and previous reports have indicated that the highest prevalence of the enzyme deficiency is in the Mediterranean region. However, there is not an investigation has been made on normal values of the enzyme in Balıkesir province that is located partly in Aegean and partly in Marmara regions of Turkey. In the present study, a total of 259 clinically healthy individuals were randomly selected and the events had leukocytosis or thrombocytosis were not included. According to quantitative test results, the normal mean values of G6PD in healthy males were 9.53 $\pm$ 8.24 IU/gHb and 247.1$\pm$ 40.6 IU/ $10^12$ RBC, in females were 9.03 $\pm$ 1.83 IU/gHb and 249.5 $\pm$ 41.74 IU/ $10^12$ RBc. The frequencies of complete and mild deficiencies were 9.7 % and 0.7 % in males, respectively, while all the events were mild deficient at the rate of 6.4 % in females. The results indicated that there is not an important statistical difference of G6PD activity between males and females in Bahkesir province. The frequency of deficients were detected as 8.49 %.