Abstract Over the past thirty years there has been considerable research into the properties of CdTe semiconductor radiation detectors. Recently, the quality of CdTe detectors has improved (notably by the substitution of around 10% of the cadmium by zinc) to the point where high quality room temperature gamma-ray spectroscopy is possible using devices of volume 1 cm 3 or greater. We are currently investigating the variation in pulse shape resulting from γ-ray interactions in CdZnTe detectors supplied by eV Products. The impact of these variations is assessed in terms of its effect on the resolution in the pulse height spectrum. Parameters studied for individual pulses include the shaping amplifier amplitude and slew rate of the preamplifier output pulse. These signals are digitised using an oscilloscope controlled by a PC using IEEE-488 data transfers. Three-dimensional plots of this data are used to observe the distribution of detector outputs. Results are shown for 3 mm × 3 mm × 2 mm thick Cd 0.9Zn 0.1. Te crystals which indicate that significant improvement in peak to background ratio can be obtained by selective histogramming of the main amplifier output pulses.