A new technique for performing a microvascular end-in-end or "sleeve" anastomosis is described. The new method utilizes two asymmetrically placed, looped sutures that do not enter the active lumen or breach the active intima. It has advantages over previous methods because it consistently saves time and because of the decrease in the number of possible technical complications. In 77 anastomoses performed in white rats by different surgeons, including a few inexperienced students of microsurgery, there was only one failure (24-hr patency). After eight practice anastomoses, the average time taken from vessel division to final clamp release in 30 procedures was 7 min 33 sec, with a standard deviation of 1 min 45 sec. The sleeve anastomosis performed by this method has shown itself to be as reliable as a conventional end-to-end suture method and has the advantages of significant time saving and minimization of intimal trauma. The anastomosis of vessels of differing sizes is facilitated by the conformation of this new method and the technique has clinical potential in the anastomoses of interposition vein grafts and in human intravenous anastomoses.