The effects of age and fat cell size on the metabolism of white human adipose tissue were analysed independently. Abdominal subcutaneous adipose tissue specimens were obtained from children varying in age from 0-15 years and from adults (mean age +/- S.D.; 38.2 +/- 14.1 years). The basal rates of lipolysis and glucose incorporation into lipids were considerably higher in children than in adults even when differences in fat cell size had been taken into account. Lipolysis in response to a maximal concentration of noradrenalin was higher in fat cells from children. However, on a percentage basis the responsiveness to this agent was similar in children and adults. Irrespective of age, glucagon did not elicit a lipolytic response. Thus, it does not seem that the increased lipolysis known to occur in vivo in the neonatal period is due to a direct effect of glucagon on white adipose tissue. However, the overall lipolytic capacity is increased in fat cells from children.