Growth retardation affects about a third of children younger than age 5 years in developing countries and is associated with poor development. Previously, we did a trial of nutritional supplementation and psychosocial stimulation in stunted children aged 9-24 months. Non-stunted children were also assessed. Both types of intervention improved development. We now present the effects of early interventions on cognition and education in 103 of the 129 stunted children and compare them with 64 of the 84 non-stunted children now aged 17-18 years. We recorded no significant effects of nutritional supplementation. Compared with no intervention, stimulation resulted in higher full scale IQ scores (coefficient 0.38, 95% CI 0.06-0.71, p=0.02) and higher scores on the verbal subscale (0.37, 0.07-0.68, p=0.02), Peabody picture vocabulary test (7.84, 0.73-14.95, p=0.03), verbal analogies (0.26, 0.03-0.49, p=0.03), and reading tests (4.73, 1.31-8.14, p=0.007, and 2.7, 1.12-4.37, p=0.001). Overall, stunted non-stimulated participants had significantly poorer scores than the non-stunted group on 11 of 12 cognitive and educational tests. Stunting in early childhood is associated with cognitive and educational deficits in late adolescence, which are reduced by stimulation at a young age.