Between July 1980 and July 1988, 478 consecutive patients underwent aortic aneurysm operations at Royal Prince Alfred Hospital. Renal function was assessed by measurement of serum creatinine levels. The left renal vein was divided in 28 (8%) of the 355 patients undergoing elective aneurysm resection. The mean immediate postoperative creatinine values were significantly higher after left renal vein division, 193 +/- 174 mumol/L, compared to 133 +/- 93 mumol/l for those whose left renal vein remained intact (p less than 0.05 by Mann-Whitney U test). After one month, serum creatinine levels had decreased but were still significantly higher in those patients in whom the left renal vein had been divided, 170 +/- 166 mumol/l, compared to those in whom it was left intact 109 +/- 49 mumol/l (p less than 0.05 by Mann-Whitney U test). The suprarenal aorta was cross-clamped in seven (25%) of the 28 patients in whom the left renal vein was divided, compared to 21 (6%) of the 327 with the left renal vein intact. A rise in creatinine level was observed after suprarenal aortic cross-clamping. The left renal vein was divided in 17 (14%) of the 123 patients having emergency surgery for ruptured aortic aneurysm, 61 (49%) of whom survived more than 30 days. The mean immediate postoperative creatinine values were significantly higher after left renal vein division, 426 +/- 277 mumol/l, compared to those in whom the vein was left intact, 178 +/- 136 mumol/l (p less than 0.05 by Mann-Whitney U test). After one month, serum creatinine levels were still significantly higher in those patients in whom the left renal vein had been divided. Although division of the left renal vein is a useful way to improve exposure of the juxtarenal aorta, the maneuver is associated with an adverse effect on renal function.