The single most important factor determing the patency of a microvascular anastomosis is the surgical precision with which it is performed. Inaccurately placed sutures, damage of the intima, exposed media and adventitia, and stenosis of the lumen at the site anastomosis all contribute to decreased patency rates. The first 50 consecutive microvascular anastomoses performed by a single microvascular surgeon were analyzed in vivo and with the scanning electron microscope. The frequency and significance of various technical errors are discussed. Scanning electron microscopy is recommended as a convenient and quick technique for assessing the evenness and accuracy of intimal apposition in microvascular anastomosis.