The rates of weight gain and urea kinetics were measured in 12 children receiving one of two energy dense, isonitrogenous formulae (711 kJ/kg/day, 170 kcal/kg/day) during recovery from severe undernutrition. Both formulations contained added arachis oil but in one a source of complex carbohydrate was added in the form of pectin (3.4% of total energy). The children taking the pectin diet had a rate of weight gain which was highly significantly less (7 g/kg/day) than the children not receiving pectin (14 g/kg/day). Urea production was significantly less on the pectin diet (0.37 +/- 0.07 vs 0.55 +/- 0.18 gN/kg/day). On the pectin diet there was a reduction in the rate of excretion of urea in urine and in the rate at which urea nitrogen was salvaged by the lower bowel, but these differences failed to reach statistical significance.