In this controlled trial we investigated the effect of an anabolic steroid, in terms of the changes in body composition that occurred in ill surgical patients requiring intravenous nutrition. Glucose was the sole non-protein energy source. The study was conducted over a 14-day study period in two comparable groups of 13 patients. The changes in body weight, fat, protein and water were measured. The control group received a nutrient solution of hypertonic dextrose and amino acids (44.8 +/- 8.2 kcal/kg/day), and the comparative group received the same solution (44.3 +/- 5.2 kcal/kg/day) and 100 mg of an intramuscular injection of nandrolone decanoate at the commencement of the study and again one week later. Over the two-week study period both groups gained body weight. In the controls this was composed of fat (0.4 kg) and water 1.5 kg). In the anabolic steroid group, weight gain was mainly water, and fat gain did not occur. Neither group gained body protein. Diuretic therapy was required more often (21 patient days compared with 5 patients days; p less than 0.001) in the anabolic steroid group to control excessive water retention. Our study has shown no benefit from an anabolic steroid when given in combination with a 14-day course of intravenous nutrition. Water retention was more of a problem with this therapy.