Abstract
This study presents the assessment of inbreeding depression on the intelligence quotient among north Indian Muslim Children of school age. The Weschler Intelligence Scale for Children (WISC-R)-74 was given to the children in both groups (50 each non-inbred and inbred of the first-cousin status), aged 6 to 11 years and from the same socio-economic status. The change of the mean follows genetic theory; however, the nature of the change in variance seems to be somewhat different.