OBJECTIVE To determine the serum concentrations of procollagen type III peptide in severely injured patients with different outcomes and to evaluate the relationship between serum procollagen type III peptide concentrations, sources of increased posttraumatic fibrotic activity (wounds, lung, liver, kidney), and decreased elimination of procollagen type III peptide (liver). METHODS Prospective study. METHODS Surgical ICU, university hospital. METHODS Fifty-seven patients (mean injury severity score: 38.5 points, range 13 to 75 points), between 16 and 70 yrs of age, treated in our institution within 6 hrs after the accident. METHODS Serial measurements were started on admission and continued on a 6-hr basis. After 48 hrs, the monitoring interval was extended to 24 hrs until recovery (but at least until day 14) or death. At each point of evaluation, pulmonary and circulatory function parameters and chest radiographs (once a day) were evaluated, the results were recorded, and blood samples were drawn to determine procollagen type III peptide, total bilirubin, creatinine, gamma-glutamyl transferase, polymorphonuclear elastase, and other parameters. Statistic evaluation was done with the Wilcoxon test, Spearman rank correlation, and a multiple regression model. RESULTS Mean procollagen type III peptide serum concentrations (+/- SD) were significantly different in patients who died (8.0 +/- 3.8 U/mL) compared with those patients who survived with organ failure (2.7 +/- 1.3 U/mL) or without complications (1.4 +/- 0.5 U/mL), respectively. Significant correlations of procollagen type III peptide concentrations with the serum bilirubin concentrations (r = .7), days with need of mechanical ventilation (r = .64), PaO2/FIO2 ratio (r = -.6), polymorphonuclear elastase (r = .6), serum creatinine concentrations (r = .55), and injury severity score (r = .33) were observed. There was a tendency toward higher serum procollagen type III peptide concentrations in patients with severe skeletal injuries. CONCLUSIONS Serum procollagen type III peptide concentrations in severely injured patients may be considerably increased in correlation with injury severity and outcome. Procollagen type III peptide serum concentrations seem to reflect the sum of increased collagen formation from wound healing and fibrogenesis of mediator-related organ damage (especially lung) and decreased procollagen type III peptide excretion due to impaired liver function. Further data are necessary to evaluate the role of hepatic elimination in these patients.