In order to explore the nature of glucose-6-phosphate dehydrogenase (G6PD) deficiency in one of the coastal provinces of the Caspian Sea (Mazandaran) in Iran, we have analysed the G6PD gene in 74 unrelated G6PD-deficient males (2-6 year children) with a history of Favism, by using PCR and subsequent digestion by appropriate restriction enzymes, looking for the presence of certain known mutations. The results showed that 49 of 74 cases (66.21%) had the G6PD Mediterranean genotype and there were not other known mutations (such as G6PD Aures, G6PD A, and G6PD A–) in rest of the samples. This is the first report on the molecular analysis of G6PD mutations in north of Iran and we have revealed the frequency and distribution of the most common G6PD variant (G6PD-Mediterranean) in this area.