&NA;Mechanical circular stapling devices offer several advantages in the formation of low rectal anastomoses. The author's aim was to compare the quality of rectal anastomoses created in dogs using the two commonly available staple suture guns, the EEA and SPTU. Thirty dogs, 15 with each gun, had rectal division and anastomosis. The first 20 dogs (ten EEA and ten SPTU) were sacrificed at eight days. Anastomotic integrity was assessed using plain x‐ray, barium enema, and postmortem examination and pressure studies. The remaining ten dogs, five in each group, were sacrificed at 48 hours, and the anastomoses were inspected and examined histologically. Eleven of 15 anastomoses in the EEA group showed evidence of breakdown compared with only three of 15 in the SPTU group (P<0.02). It is concluded that the SPTU gun created a more satisfactory anastomosis and that this was probably due to its staples having an adjustable closure.