Differential scanning calorimetric (DSC) studies were carried out on xerographic photoreceptor materials of amorphous selenium (a-Se), a-Se1∃-xTex and a-Se:0.5 wt% As alloys with various amounts of chlorine doping. Glass transformation kinetics of bulk and vapour-deposited film samples were essentially identical indicating a similar amorphous structure for both forms. The glass transition temperature,Tg, in the a-Se1∃-xTexsystem was found to increase monotonically with the tellurium content up to ∼13 wt% which was accompanied by a fall in the activation energy,Egl, for the structural relaxation. 0.5wt% As increasedTg, whereas chlorine doping in the amounts used (∼100 ppm) had no effect onTg. Crystallization exotherms were analysed using the Kissinger method which was shown to remain a valid analysis by integrating the fundamental Kolmogoroff equation describing crystallization transformations by nucleation and growth. The signifiance of the activation energy,EA, and the frequency factor,C0, in the Kissinger analysis is discussed and used in interpreting the different crystallization behaviour exhibited by the various alloys. The apparent activation energy,EA, of the crystallization kinetics was found to fall with the temperature range accessed in the DSC experiment. When other authors' previous crystallization studies by other methods were also considered, then 1/EA was found to fall nearly linearly with the mean reciprocal temperature, 〈1/T〉, used in the experiment. It is argued that this behaviour arises if the crystal growth rate scales with the inverse viscosity of the melt and the latter is described by a Vogel-Tammann-Fulcher type of behaviour. The additives tellurium and arsenic retard the crystallization essentially by increasing the viscosity. Chlorine doping was also found to have an inhibitory effect but due probably to a change in the nucleation kinetics, rather than a viscosity rise.