Abstract. Biopsies of subcutaneous adipose tissue were taken from children varying in age from a few hours to 15 years. In 63 children the cell diameter was determined. Weight in relation to height was normal. At an average the fat cell weight was 0.05 μg in the new-born, but adolescent values were reached within the first year of life. Biopsies from 23 children were incubated for one week in vitro. Cell size was not changed significantly during this period. Glycerol release was strongly correlated to cell size and the long-term effect of insulin on the lipolysis was found to be stimulating as previously shown for adults. At the same cell size basal lipolysis was higher in children below one year of age than later in life. It is concluded that the tissue culture method may be used for studies of adipose tissue from children. Furthermore, the data indicate that there is a difference in adipose tissue metabolism and cell size of children below one year as compared to older children and adults.