Microvascular techniques are important in making routine anastomoses quicker and difficult anastomoses easier. The authors have developed three types of sleeve anastomoses for different size vessels: a three-stitch sleeve anastomosis, four-stitch sleeve anastomosis, and sidecut sleeve anastomosis. Arteriography, in vivo observation, pulsed ultrasound Doppler hemodynamic study, histology, and ultrastructural examination with scanning electron microscopy at 2 to 90 days demonstrated that all three groups of sleeve anastomoses do not stenose, do not show hemodynamically significant vasospasm, and are not complicated by aneurysm formation by 90 days. The hemodynamics were comparable to control sutured anastomoses at 2 to 4 hr postoperatively. The sleeve anastomoses left no suture material within the vessel lumen. Reendothelialization was comparable with controls at 14 days, and the long-term patency rates were similar (p > 0.05). The operative times for all three types of sleeve anastomoses were significantly shorter than sutured control anastomoses (p < 0.001). Although limited by available vessel length and diameter, the sleeve anastomosis is a useful technique for the microsurgeon.