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Background & objectives: Screening for Fragile X syndrome (FRAXA), the most common genetic cause for mental retardation (MR), has mostly been carried out among MR patients. The present study was conducted to find out prevalence of FRAXA amongst children residing in the rural areas of West Bengal. Methods: Demographic details including age, sex, nutritional status as well as birth, medical and developmental histories, were collected amongst rural children (n=38,803) of West Bengal, India, over three years (2004-2007). Based on the records of scholastic backwardness, 179 children were short-listed and examined by a team of experts comprising of child psychiatrist, clinical psychologist, paediatrician and special educator. Blood samples were collected and molecular and cytogenetic studies were performed for identification of CGG repeats and determination of FMR1 gene promoter methylation. Results: Of the selected 179 children, six were diagnosed as Down syndrome, one as cerebral palsy and 140 as non-syndromic MR. These 140 children with MR were grouped as mild (56), moderate (60), and severely (4) retarded based on IQ; children <5 yr were grouped as developmental delay (20). FRAXA was not detected in any of these children (frequency being 0% with 0-.02% confidence interval). Prevalence of MR was found to be low (about 4/1000 children). Down syndrome also had a lower frequency (0.15/1000 children). Interpretation & conclusion: The data obtained in the present study indicated that familial disorders like FRAXA were less frequent in the studied population. [ABSTRACT FROM AUTHOR]