Objective: Glucose 6-phosphate dehydrogenase(G6PD) deficiency manifests genetic polymorphismand prevalence of its varying among geographicregions and ethnic groups. G6PD deficiency isimportant in Gaziantep, Turkey because high deficiencyprevalence was observed in Adana and Antakya, theneighbouring  Mediterranean cities.Methods: In this study, sera from 306 subjects (166female, 140 male) between 1-80 years old were forerythrocyte G6PD activity with International Committeefor Standardization in Hematology (ICSH) method. Afterexcluding the outliers, 95 % interpercentile interval wasaccepted as reference limit.Results: In Gaziantep reference group erythrocyteG6PD activity limits for subjects over one year old are6.4 - 13.2 U/ g Hb, 30ºC. Seven subjects with low enzymeactivities indicate that G6PD deficiency frequency isapproximately 2.3  ± 1% in Gaziantep.Conclusion: G6PD deficiency frequence isapproximately 2.3 ± 1 % in Gaziantep which is higherthan the mean prevalence in Turkey.Key words:  Glucose 6-phosphate dehydrogenase,reference limits, deficiency frequency