The neonatal screening programs had been succeeded in prevention of mental retardation due to congenital hypothyroidism through early detection and treatment. The aim of the present study was to evaluate physical and mental development of children with congenital hypothyroidism aged 3 years and above who were early detected and treated through neonatal screening program at Alexandria Governorate, then comparing them to normal children. The study was comparative cross section study that included 58 cases and 170control.All children were assessed mentally, socially and physically. Data were collected by predesigned data collection sheet. The results showed significant statistical difference between cases and control in certain mental and physical aspects.