The relationship between wound healing and skin prolylhydroxylase activity was examined in 212 patients undergoing reconstructive procedures and 109 controls using skin prolylhydroxylase activity as an index of collagen synthesis. In the control group, the median value of skin prolylhydroxylase activity was 360 cpm/mg protein. There was a higher skin prolylhydroxylase activity in 274 patients with successful healing (368 cpm/mg protein) than there was in 33 patients who required local wound care (202 cpm/mg protein) and 14 patients with severe local complications (71 cpm/mg protein, p = 0.02). Skin prolylhydroxylase activity was also significantly lower (p = 0.002) in patients with laboratory criteria for malnutrition (albumin < 3.5 g/dl, 108 cpm/mg protein; total lymphocyte count < 1,500 mm3, 211 cpm/mg protein, and albumin < 3.5 g/dl + lymphocyte count < 1,500 mm3, 52 cpm/mg protein), but age, diabetes mellitus, malignancy and wound infection did not affect skin prolylhydroxylase activity. These results suggest that skin prolylhydroxylase activity is reduced in patients with malnutrition and delayed wound healing.