&NA;To study new collagen formation in the healing of anastomoses in the right colon, five male Sprague‐Dawley rats had single‐layer colonic anastomosis performed. Five additional rats had suture of the colon with interrupted sutures without transection of the colon. Ten animals served as controls. One week after surgery, animals were given3H‐proline repeatedly to label new collagen formation during the second and third weeks. Animals were sacrificed three weeks after suturing or anastomosis. Two‐ or 10‐mm segments were precisely excised on either side of the suturing or anastomoses. Total collagen and its total radioactivity were measured per segment. Collagen hydroxyproline and its radioactivity increased (100 per cent) only within 1 cm of the anastomosis or suture alone. No local or distant decrease in collagen was observed. Collagen formation in colonic wounds appears to be a local process.