Introduction: Congenital hypothyroidism (CH) is the most common cause of preventable mental retardation. The course of the disease can be silent and may cause serious health problems when the diagnosis is delayed. "Screening Program for CH" has facilitated early diagnosis and treatment preventing severe complications. Materials and Method: The records of the 140 patients with CH were retrospectively analyzed. The patients with CH were compared before and after the screening program. Results: Of the 140 cases, 74 (52.9%) were female and 66 (48.4%) were male. The clinical presentations of the patients with CH were jaundice (32.1%), constipation (32.1%), referral due to high TSH (25.7%), and growth retardation (10.7%). The etiologies of CH based on scintigraphic imaging of the thyroid gland (32 cases) were thyroid dyshormonogenesis in 43.7%, thyroid agenesis in 43.7%, and ectopic thyroid in 12.6%. The mean age at diagnosis was 292±632 days (370.9±704.6 days before screening, 35.2±48.3 days after screening). A total of 36 patients were diagnosed with mental retardation (35 were diagnosed prior to screening). Mean height SDS of patients diagnosed after screening program was significantly higher than that of those diagnosed before screening program (p=0.02). Mean serum TSH, TT4, and FT4 at admission were 144.8±227.1 mIU/ml, 4.92±4.44 mcg/dl, and 0.63±0.41 ng/L, respectively. Conclusions: Significant reduction in the number of patients with mental retardation after the screening program shows once again the importance of this program. © The Journal of Current Pediatrics.