Free catecholamine (epinephrine + norepinephrine) excretions of normal male infants 2.1-3.2, 4.5-10.6, and 12.5-18.5 months of age, respectively, and of infants and children with marasmus or marasmic kwashiorkor were measured on three consecutive days after admission and after partial rehabilitation. In normal infants, particularly the older ones, the first day's excretion was higher than that of the next two days, probably in response to the stress of the procedures. There was an increase with age, but on a surface area basis, the differences were not significant, the three age groups excreting 15.1 plus or minus 10.2, 23.8 plus or minus 20.9, and 24.7 plus or minus 14.3 mug/m-2/day, respectively. Excretions of marasmic infants on admission were not significantly different from those of the control children. Higher mean values were due to elevated excretions of infants with severe infection. After partial rehabilitation, excretions were similar to those of control subjects. In children with marasmic kwashiorkor excretions were no different from those of control infants, except in severely infected children. Admission values revealed more day-to-day variation than recovery values or than those of normal and marasmic infants, in whom subject to subject variation was more marked.