Studies in Europe [1], India [3] and America [4] have shown that birth weight and weight at 1 year of age correlate with glucose tolerance. Thus, factors affecting birth weight and infant growth such as fetal and neonatal nutrition, seem to play a part in the aetiology of glucose intolerance and Type II (non-insulin-dependent) diabetes mellitus.These findings have been used as supportive evidence for the thrifty phenotype' hypothesis [5] which proposes that the fetus selectively apportions nutrients, channelling' them to essential organs such as the brain and heart during times of poor nutrition at the expense of peripheral organs like the pancreas. Poorer pancreatic development with a smaller complement of islet endocrine cells and, possibly, changes in tissue insulin sensitivity means that whilst a person remains in an environment where nutrients are scarce there is no adverse effect. When exposed to conditions of increased nutrition however, the pancreatic beta cell complement is unable to meet the biochemical demands and glucose intolerance and Type II diabetes can result. Those at greatest risk of developing Type II diabetes are those born with low birth weights who develop a high BMI [4].The combination of low birthweight and subsequently high BMI is characteristic of populations undergoing cultural and economic shifts towards first- Diabetologia (1998) Summary A number of studies have shown that glucose tolerance falls with decreasing birth weight and that people with low birth weight and high body mass index (BMI) as adults are those at greatest risk of developing Type II (non-insulin-dependent) diabetes mellitus. No such studies have been carried out in African populations. Therefore we investigated the relation between glucose tolerance and birth weight in a group of 7-year-old black South Africans for whom longitudinal anthropometric data were available. Oral glucose tolerance tests (OGTTs) were carried out on 152 subjects and inverse correlations were found between birth weight and the total amount of insulin secreted during the first 30 min (r = ±0.19, p = 0.04) and last 90 min (r = ±0.19, p = 0.04) of the oral glucose tolerance test and also between birth weight and the 30 min glucose concentrations (r = ±0.20, p = 0.02). Children born with low birth weights but who had high weights at 7 years had higher insulin concentrations and indices of obesity compared with those with low birth weights and low weights at 7 years. There were also positive correlations between weight velocity and BMI (r = 0.24, p = 0.02) and weight velocity and insulin resistance (r = 0.18, p = 0.04) as measured using homeostasis model assessment (HOMA). Thus, low birth weight in conjunction with rapid childhood gains in weight especially as subcutaneous fat, produces poor glucose tolerance in 7-year-old children and can make them susceptible to the development of Type II diabetes later in life. [Diabetologia (1998)