Abstract Twenty-two adult mongrel dogs underwent small bowel anastomoses. Single-layer everting, single-layer inverting, and double-layer inverting anastomoses were compared by in vivo angiograms and microangiography. The single-layer inverting anastomosis emerged as the best vascularized, closely followed by the double-layer inverting anastomosis. The single-layer everting anastomosis appeared to develop cross-circulation late and poorly. We believe, supported by this and other studies, that the single-layer inverting anastomosis has advantages over the double-layer inverting anastomosis. By contrast, the everting type of anastomosis produced a significant degree of technical failure which may well be related to the differences in microcirculation found in this study.