Tests were performed on a Westinghouse model MO-120C capacitor discharge mobile x-ray machine to determine accuracy of voltage indications, the relationship between voltage setting and current-time, line voltage effects and current drain, exposure reproducibility, focal spot size and location, correspondence between the collimator and light localizer, inherent filtration, half-value layer, radiation output, and tube housing and collimator leakage. Spurious radiation was found to originate in the tube under certain conditions. These conditions were investigated, and the observed radiation levels are reported. (BRH/DEP)