We have measured both the current response and the pulse response of a microchannel plate, MCP, to X-rays incident at an angle of 45° in the energy range of 8 to 100 keV. The X-ray detection efficiency, pulse height distributions, and sensitive depth of the MCP were determined from these data. We find that detection efficiency extrapolates to zero below 8 keV, and ranges between values of 1% and 2.6% above this energy, much higher than anticipated from previous measurements for oblique incidence below 6 keV. When compared to previous measurements at higher energies, we conclude that MCP's have a relatively constant detection efficiency in the energy range 10 to 600 keV, which is a rather unique property as compared to other X-ray detectors. We find that the shape of current response curves differs somewhat from the shape of efficiency curves, that pulse height distributions are proportional to pulse height to the -1.1 to -1.6 power, and that 90% of the current ori-ginates in the first 25 to 30% of the MCP thickness.