A new method for investigating microchannel plate quality is described. The microchannel plate is operated with an applied voltage, either with normal or reverse polarization. Without any polarization, the scanning electron microscope takes a picture only of the external flat face. With a reverse voltage, the secondary electrons may be collected from the full depth of the channel and give a clear and bright picture of the internal surface of the channel. With normal polarization, the secondary electrons are multiplied through the plate and give the image of the electron gain of each individual channel. This use of the SEM is therefore very helpful for studying the quality of the microchannel array.