Currently there is much interest in stabilized amorphous selenium (a-Se alloyed with 0.2–0.3% As and doped with 5–20 ppm Cl) as an x-ray photoconductor in various x-ray imaging systems. Although optical photogeneration in a-Se is well characterized, experiments on its x-ray sensitivity have been limited and, further, have resulted in widely differing conclusions especially for the electron hole pair (EHP) creation energy EEHP. In this work, we first introduce absolute and incremental sensitivity (S and s, respectively) concepts within the electrostatic readout mode of operation and then establish models linking these two sensitivities to the energy EEHP absorbed to create a free EHP. X-ray irradiation induced xerographic discharge experiments have been carried out on vacuum deposited stabilized a-Se x-ray photoconductor films to examine how the sensitivity depends on the charge carrier schubwegs (μτF where μ is the drift mobility, τ is the lifetime, and F is the electric field), the mean photon energy, and the detector thickness L. Experiments indicate that unless both electron and hole schubwegs are much longer than the photoconductor thickness, the sensitivity is reduced. The efficiency of EHP generation per absorbed x-ray photon, i.e., the apparent energy absorbed per free electron hole pair EEHP has been determined as a function of electric field and mean photon energy. EEHP decreases with increasing applied field and energy. By examining EEHP vs 1/F and extrapolating to 1/F=0, a saturation value EEHP0 for EEHP is predicted and estimated (4 to 6 eV) which, within experimental errors, is close to the theoretical expectation of ∼2.2Eg and substantially smaller than previously reported values for EEHP0 (18–29 eV).