The developmental sequelae of infant failure to thrive (FTT) were examined in an unreferred group of 6-year-olds with a history of severe nonorganic growth retardation, sampled from a 1-year birth cohort in an inner-city area of South London. Children who failed to thrive in infancy (weight below the third centile for at least 3 months) and their pairwise matched comparisons were originally studied at 15 months, and 42 cases and 42 controls (89.5% of the sample) were followed up. At 6 years, previously growth-retarded children were considerably smaller than matched comparisons, in terms of body mass index (BMI), and height and weight for age z scores. History of FTT explained substantial variance in weight and BMI at 6 years, with maternal height also contributing to variation in height for age. Child cognitive functioning at 6 years was examined using the McCarthy Scales: cases had more limited quantitative and memory skills than comparisons, but there was no intergroup variation in general cognitive performance. In contrast to analyses of physical development, failure to thrive did not account for cognitive functioning; maternal IQ was the sole significant predictor of performance on all indices of child cognitive abilities. At 15 months, earlier growth faltering was linked to limitations in mental development, but these findings were not confirmed by the follow-up data: the timing of FTT was not related to cognitive abilities at 6 years. Results correspond to past research indicating that nonorganic failure to thrive is associated with persistent limitations in physical stature. There was little evidence of cognitive disadvantage for case group children at school age, suggesting that the adverse effects of early malnutrition on cognitive functioning appear to diminish over time.