This study evaluated the contribution of prenatal, perinatal, neonatal, and postnatal factors to the prevalence of cognitive disabilities among children aged 2-9 years in Bangladesh. A two-phase survey was implemented in 1987-1988 in which 10,299 children were screened for disability. In multivariate analyses, significant independent predictors of serious mental retardation in rural and urban areas included maternal goiter (rural odds ratio (OR) = 5.14, 95% confidence interval (CI): 1.23, 21.57; urban OR = 4.82, 95% CI: 2.73, 8.50) and postnatal brain infections (rural OR = 29.24, 95% CI: 7.17, 119.18; urban OR = 13.65, 95% CI: 4.69, 39.76). In rural areas, consanguinity (OR = 15.13, 95% CI: 3.08, 74.30) and landless agriculture (OR = 6.02, 95% CI: 1.16, 31.19) were also independently associated with the prevalence of serious mental retardation. In both rural and urban areas, independent risk factors for mild cognitive disabilities included maternal illiteracy (OR = 2.48, 95% CI: 0.86, 7.12), landlessness (OR = 4.27, 95% CI: 1.77, 10.29), maternal history of pregnancy loss (OR = 2.61, 95% CI: 0.95, 7.12), and small for gestational age at birth (OR = 3.86, 95% CI: 1.56, 9.55). Interventions likely to have the greatest impact on preventing cognitive disabilities among children in Bangladesh include expansion of existing iodine supplementation, maternal literacy, and poverty alleviation programs as well as prevention of intracranial infections and their consequences. Further population-based studies are needed to confirm and understand the association between consanguinity and serious cognitive disability.