To identify the causative factors responsible for mental handicap. Institutional based cross sectional study was carried out in 165 mentally Challenged students of Nandanwan School Nagpur from March 2004 -May 2005. Causative factors were identified on the basis of history obtained from mothers, detailed examination of children and hospital and medical documents. Out of the 165 children Down's syndrome was causative factors in 21(12.73%), prematurity in 20(12.12%), febrile convulsions in 18(10.91%), seizures in 15(909%), Birth asphyxia in 14(8.48%), familial in 12(7.27%) cases. In 34 (20.61%) cases causer was not known. Only prenatal causes were responsible in 39(23.64%), only perinatal in 30(18.18%), and only postnatal 36(21.82%) cases. Rest causes were in combinations. The Common causative factors for mental handicap were Down's syndrome, prematurity, seizures, febrile convulsions during early developmental period. In addition, maternal age above 30 years was found to be a strong risk factor for Down's syndrome.