The crystallization kinetics of glassy Co78Si13B9 (primary), Pd80Si20, Fe80B20 (eutectic) and Co75B25 (polymorphic) have been studied with differential scanning calorimetry and analysed with non-isothermal theoretical expressions. The analysis gives good agreement with isothermal studies in the polymorphic case and in the eutectic Fe80B20, with accurate values of the activation energy and Avrami index. Two superimposed peaks, related to surface and bulk nucleation, have been found in the eutectic alloy Pd80Si20. Although the separation of the parameters of each peak is very difficult, the second one can be fitted to a non-isothermal equation, with activation energy very close to the isothermal values reported in the literature. A better fit of the observed behaviour is found using a Vogel-Fulcher rate constant in this alloy. The primary crystallization is driven by diffusion processes, and does not fit the Avrami equations. This results in long tails of the non-isothermal peaks which cannot be analysed accurately with the usual methods. The kinetic parameters of all the alloys change with temperature, indicating that, even when a good fit is obtained, the usual expressions for non-isothermal analysis are only valid in narrow ranges.