The effects of controlled continuous nasogastric tube feeding with a non-elemental liquid diet (Nutrison high energy) were studied 1 day before, and 1 week and 3 weeks after radical surgery mostly for cancer of the tongue or floor of the mouth in 20 patients. Since the actually administered 89% of a planned dose of 32 kcal/kg body weight/day given to the first eight patients (group A) proved inadequate to prevent a decrease of body fat mass, the energy dose given to 12 successive patients (group B) was increased. The administration of 95% of 43 kcal/kg body weight/day to group B patients appeared to be sufficient. A marked decrease of the 24 h urinary excretion of creatinine and 3-methylhistidine was observed at 1 week and still existed at 3 weeks after operation in both groups. The decrease was significant in group A amounting to some 40% for both metabolites. In group B creatinine excretion decreased by some 20% (n.s.) and 3-methylhistidine by some 35% (n.s). These findings suggest diminished muscle protein breakdown, even in the presence of an ample nutritional supply of energy and protein. A transient decrease of serum albumin, iron and zinc in all patients is likely not to be related to nutritional intake, but to surgery itself. Analysis of trace minerals and vitamins in blood and amino acids in serum and urine showed no deficiencies or amino acid imbalance. Assessment of the psychosocial impact of the nasogastric tube feeding regimen revealed gastro-intestinal complaints in a minority, and feelings of being deprived of the act of eating and drinking in the majority of patients.