Eight plasma proteins, four anthropometric measurements, and 21 amino acids were measured in 24 fasting patients before surgery. A matrix of partial correlation coefficients, correcting for age and height, showed many correlations including several between biochemical and anthropometric data such as between valine or prealbumin and arm muscle circumference. Valine was the most highly correlated variable and was used to rank and group the patients. Ten patients with low valine had the greatest weight loss and also had low values for 18 variables which could be subdivided. 1) Thirteen of the low variables were interrelated and correlated with valine, i.e., arm muscle circumference, prealbumin, retinol-binding protein, transferrin, haemoglobin, isoleucine, leucine, methionine, phenylalanine, tyrosine, serine, alanine, and proline. 2) Fat, threonine, glycine, and beta-lipoprotein were interrelated with one another but not with the larger group. Only beta-lipoprotein were interrelated with one another but not with the larger group. Only beta-lipoprotein correlated with valine. It is suggested that variables in both groups reflect protein-energy malnutrition but that those in the second group are affected predominantly by energy intake.