The prevalence of genetic diseases and congenital malformation in the Israeli Arab community is relatively high, but its distribution is not uniform. The aim of this study was to estimate the frequency of mental retardation disorders in children living in 5 Israeli Arab villages and determine its association with consanguinity. Mental retardation was found to affect 300 children in the screened population, yielding an overall prevalence of 14.5 per 1000. Most of those affected (68%) were the offspring of consanguineous marriages. One village with a high prevalence (4.3%) of neurological hereditary diseases was studied in detail. The prevalence of neurological hereditary diseases and mental retardation associated with consanguinity in these children highlights the need to implement appropriate preventive program.