The utilization of exogenous urea as a nitrogen source was studied in 10 malnourished adults. Urea administration induced a significant positive nitrogen balance in all cases. In three subjects increasing doses of urea nitrogen induced a corresponding rise in positive nitrogen balance. Neomycin administration produced a slight decrease in urea nitrogen retention, apparently due to an increased fecal nitrogen loss during neomycin induced diarrhea. An increased supply of dietary protein as well as an improved nutritional status were shown to abolish the need for utilization of urea nitrogen. Intravenous urea administration in two subjects demonstrated similar effects to those obtained through oral route of administration.