Somatomedin activity was assayed in the plasma of children suffering from protein calorie malnutrition by a bioassay using rat cartilage and expressed as sulphate uptake ratio. The sulphate uptake ratio was particularly reduced in kwashiorkor. In marasmus there was a slight reduction and the levels were still in the normal range. Plasma growth hormone (GH) levels were raised in kwashiorkor but were in the normal range in marasmus. Reduction in sulphate uptake ratio was observed only when plasma albumin levels were less than 2.5 g/100 ml (25 g/l). A rise in plasma GH was also observed but only below this threshold level.