Local energy metabolism in healing colonic anastomosis was studied in rats. A one-layer, inverting colo-colostomy was performed and frozen sections from the anastomotic area were enzyme-histochemically stained for key enzymes in energy metabolism. Anaerobic metabolism prevailed in the anastomotic area during the first postoperative week. The repair tissue between the inverted colonic leaves showed the first sign of aerobic glycolysis 1 week postoperatively. Increasing lactate dehydrogenase activity, however, was seen from day 3 onwards (simultaneously with revascularization), and indicators for amino acid metabolism, lysosomal activity and metabolism via the pentose phosphate shunt were present even earlier--from day 1 onwards. Anastomotic surgery was followed by severe reduction of metabolism in all layers of the colonic wall 0-5 mm from the anastomotic line. Normal metabolism was not restored until postoperative day 21. These findings should be considered in surgical techniques and post-operative management.