Galactosemia is an autosomal recessive metabolic disease. Galactosemia results from mutation in 3 genes but the common mutation is identified in Galactose 1- phosphate uridyl transferase (GALT) gene.G-1-phosphate levels increase in the disease that is detectable in 3-6 day old neonates and the main complication is mental retardation. Methods: We collected data from 24000 newborn babies from Fars Province, Southern Iran. The enzymatic calorimetric test was done on their blood and Red questions from the children's parents. For treatment, free lactose milk or Soya milk have been used for newborn feeding. Findings: The prevalence of Galactosemia in Fars province was 5:24000 in neonates, being more than those reported in White race and Asians. Maximum clinical symptoms before diet in 10 days after birth were vomit and jaundica and maximum clinical symptoms after using diet were sepsis full fontanelle and hepatic failure. Conclusions: The number of familial marriage in children's parents was very high. Consanguineous marriage is a major cause of inheritance of the disease in Iran. Screening should be executed for all of families with a history of Galactosemia in Iran. To the best our knowledge, this is the first large study report from prevalence of Galactosemia in Iran.