Studies in Britain have shown that adults who had a low birthweight have high plasma glucose concentrations 30 and 120 min after an oral glucose load, and an increased risk of Type 2 diabetes and impaired glucose tolerance. Both Type 2 diabetes and low birthweight are common in India. To determine whether low birthweight is associated with reduced glucose tolerance in Indian children, glucose tolerance tests were carried out on 379 4-year-old children, whose birthweights were recorded, in Pune, India. Among 201 children who had been looked after on the routine postnatal wards at birth, those with lower birthweights had higher plasma glucose and insulin concentrations 30 min after an oral glucose load, independently of their current size (p = 0.01 and 0.04, respectively). Mean glucose and insulin concentrations were 8.1 mmol l-1 and 321 pmol l-1 in children whose birthweight had been 2.4 kg or less, compared with 7.5 mmol l-1 and 289 pmol l-1 in those who weighted more than 3.0 kg. Among 178 children who had been looked after in the Special Care Baby Unit, those with lower birthweights also had higher plasma insulin concentrations at 30 min but there were no trends with plasma glucose. Our findings suggest that Indian children with reduced intra-uterine growth have reduced glucose homeostasis after a glucose challenge. This is consistent with the hypothesis that Type 2 diabetes mellitus in India may be programmed in fetal life.