The development of a snow routine for the HBV-2 rainfall-runoff model is described. Experiences from field investigation that have contributed to the work are briefly discussed. In the snow routine, snow accumulation and snowmelt are simulated using daily totals of precipitation and mean daily temperatures. The application of the model to a 2178 km2 forested basin in central Sweden is shown. A critical study of the interaction and effects of the parameters is carried out.