In order to study the replacement of vessels by biological vascular prostheses in microsurgery, an improved method for scanning electron microscopy preparation which is rapid and minimizes artifacts was developed. To limit endothelial surface injury, the vessel and prosthesis unity is, at first, prefixed by injection into one end of a 2.5% isotonic solution of glutaraldehyde. After fixation by osmium tetroxide, the samples are dehydrated by a graded series of acetone solutions and critical point dried. They are then trimmed around each suture line to pieces of 1 cm including 1/3 vessel and 2/3 prosthesis for further orientation and sectioned longitudinally, with a new razor blade, for microvascular anastomoses observations. The same chemical treatment applied to samples for transmission electron microscopy studies permitted verification of the good preservation of the cellular structures.