Results are tabulated for 12 metabolism periods of 5 days in which nitrogen and fat balances were measured in 4 children admitted to hospital from 4 to 10 weeks before the first period. The principal source of protein was milk, acid whole in 3 periods, half-skimmed in 1 and skimmed in 8 periods. Protein intake ranged from 2.6 to 9.4 g. per kg. bodyweight and, when recovery was good, nitrogen retention ranged from 16 to 53 per cent. and, per kg. bodyweight daily, from 95 to 259 mg. Nitrogen retention per kg. daily was not related to protein intake or to nitrogen absorption. Intake of fat ranged from 0.4 to 3.6 g. per kg. and absorption from 32 to 88 per cent.-D. Harvey.