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Background and purpose: The congenital hypothyroidism (CH) is the most common preventable cause of mental retardation. The incidence rate of the disease is different in various societies, but it is reported in approximately 1 per 3000-4000 births. The purpose of this study was to determine the epidemiological features of congenital hypothyroidism in Qazvin province. Material and methods: This cross sectional, descriptive study was conducted in 141 infants hospitalized with hypothyroidism who were selected through census sampling in 2011-2012 in Qazvin province. The data was collected through patients’ files obtained from health deputy department and analyzed in SPSS. Results: The patients were 63 girls and 87 boys. No significant relationship was seen between initial TSH and sex, weight, and type of childbirths. The rate of CH was observed to be more in winter, while the lowest rate of the disease was seen in spring. No significant relationship was found between the prevalence of disease and sex of the newborns and season of birth. Most patients had normal body weight. The parents of 45 infants had consanguineous relationships. Among the newborns 43 were rural and 98 were urban. In 69.5% of the cases sampling was done between 3 to 5 days after birth. The mean time for starting treatment was 33.62 days. The incidence rate of CH was 24.3 and 3.49 per thousand live births in 2011 and 2012, respectively. Conclusion: High incidence of CH in Qazvin providence signifies the need for continuous screening and complementary studies to identify probable risk factors.