OBJECTIVE We quantified the degree of preservation of renal function after reconstruction of traumatic renal injuries and identified the factors that influence preservation. METHODS We reviewed the records of 52 patients between 1977 and 1995 who underwent radionuclide scintigraphy an average of 11.4 days after renal reconstruction for trauma. Of the injuries (75% penetrating and 25% blunt) 6% were grade 2, 43% grade 3, 49% grade 4 and 2% grade 5. RESULTS On the reconstructed side mean renal function was 39.3%. Adequate preservation was possible in 42 patients (81% overall), while 10 (19%) had less than a third function on the injured side. CONCLUSIONS Our results provide quantitative evidence that renal reconstruction successfully preserves functioning renal tissue and is an appropriate method of treating major renal trauma. Preservation of functioning renal parenchyma is less successful in patients with renovascular trauma and severe concomitant injuries with shock and extensive blood loss.