Accurate determination of diagnostic x-ray spectra requires, among many other technical considerations, correction of the experimental data for the energy-dependent response of the x-ray detector. In this study, we investigated the energy response of three types of detectors (intrinsic germanium, lithium-drifted silicon, and sodium iodide) commonly used in the diagnostic energy range. We used a Monte Carlo simulation technique to compute photopeak efficiencies, escape peak losses, and Compton fractions as a function of incident x-ray energy for a variety of detector thicknesses and diameters. Calculated responses were compared with experimental results obtained for the Ge and Si(Li) detectors. The measurements, in which we used fluorescent x ray to simulate the monoenergetic beams assumed for the calculations, indicate good agreement between theoretical and experimental approaches. Techniques for correction of measured spectra for the known response of the detector were also evaluated.