The relationship between nutritional state and wound healing was examined in 66 adult surgical patients. Wound-healing response was assessed by measuring the collagen content (hydroxyproline) of fine tubes of Gore-tex inserted subcutaneously along standardized needle track arm wounds. After a period of 7 days, the tubes were removed and it was found that there was a higher hydroxyproline content in the tubing of 36 normally nourished patients than there was in the tubing of 21 patients with mild protein energy malnutrition (p less than 0.01) and 9 patients with moderate to severe protein energy malnutrition (p less than 0.01). There was no difference in the wound-healing response between the two latter groups of patients who had significantly different degrees of malnutrition. The results suggest that a definite abnormality in the wound-healing response exists in malnourished surgical patients, but it occurs earlier in the course of the illness than previously supposed.