Spatial variation of snow cover in Sweden has been very little studied up til now. This is quite remarkable as snow plays a predominant role in runoff formation in the whole of Sweden. In operational practice today the snow cover is calculated as accumulated precipitation for periods with temperatures below zero. Errors of snow measurements from precipitation gauges are very large and that is why the accumulated precipitation gives only rough estimates of the actual snow cover. Snowmelt periods during winter make it necessary to include a snowmelt procedure into calculations, which introduces a further source of uncertainty. Snowdepths are measured in connection with precipitation measurements but are not completed by information about water content, so important for hydrologists. The present practice can give acceptable results in certain regions with stable climate conditions and forests i e in the woodlands of Norrland. For other parts of Sweden i e for the mountain region and the south of Sweden the present practice is doubtful.