In a study of men aged 59 to 70 years plasma glucose levels 30 min and 2 h after a 75-g glucose load were inversely related to birthweight. To determine whether there are similar relations at a younger age the 30-min plasma glucose levels of 40 men aged 21 years, who were born in one hospital in the United Kingdom, were measured. Lower birthweight was associated with higher 30-min plasma glucose levels. This trend was independent of gestational age, and current body mass, height and social class.