The effect of glutamine-supplemented total parenteral nutrition was studied in 18 neonatal piglets (1.97 kg, 3 d old) for 8 d. They were grouped as follows: total parenteral nutrition with 0 (controls), 5 or 10 g glutamine/100 g total amino acids. Live weight gain (g/d) tended (P < 0.07) to increase with supplementation (129, 143, and 166 [SD = 20] for control, 5% and 10% glutamine), but there was no effect on total gain (g) in body protein (180, 171, 197; SD = 25), fat (135, 126, 143; SD = 33) or ash (13, 13, 16; SD = 5) for control, 5% and 10% glutamine groups, respectively. Total body water gains were significantly higher in the 10% group than in controls, with the 5% group showing intermediate gains (control = 696 g; 5% glutamine = 822 g, 10% glutamine = 970 g, SD = 119). Increased glutamine supplementation was accompanied by a trend (P < 0.08) toward increasing total body chloride space, an indicator of extracellular volume, explaining, in part, the observed differences in water gains. These results indicate that glutamine may not be a conditionally indispensable amino acid for the neonate on total parenteral nutrition. Furthermore, glutamine supplementation to total parenteral nutrition leads to disturbances in water balance that could cause increased accumulation, particularly in the extracellular space.