Muscle water and electrolytes were studied preoperatively in 22 patients with gastric carcinoma. Compared to controls, extracellular water and hence total muscle water was increased, but intracellular water was normal. Muscle sodium and chloride levels were increased in these patients while potassium and magnesium levels were normal. Based on nutritional assessment the patients were divided into wellnourished (group I, n = 7) with no or minor signs of malnutrition and malnourished (group II, n = 15) with signs of pronounced malnutrition. The wellnourished patients had normal content of muscle water and electrolytes, while in the malnourished an increase in total water, sodium and chloride in muscle tissue was found. The difference between the two groups, could be explained by malnutrition alone, since tumour size, histology, metastatic spread and operability did not differ between the two groups. A negative correlation was found between total water and both albumin and creatinine-height index which further indicates a close relationship between nutritional status and muscle water and electrolytes. In addition these findings revive the interest in nutritional assessment as a simple way of identifying metabolically deranged patients.