The Himalayan state of Sikkim (7096 sqkm) has large concentration of snowfields and glaciers. Mapping and monitoring of seasonal snow cover and glaciers using field methods are very difficult in a mountainous terrain, like the Himalayas .Therefore remote sensing techniques have been used to monitor seasonal snow cover . The Sikkim Himalayan ranges feed river Tista of its fresh water, influencing the life pattern and economy of the Sikkimese and others in Eastern India. Seasonal snow cover is one of the important natural resources of the Himalayas. Snow Cover represents a major storage of fresh water, which is released during the spring-melt period. The high surface reflectivity of snow makes albedo and area study an important component of earths radiation balance. The study shows distribution of snow cover in Sikkim and two sub basins- Tista and Rangit for 4 years; from 2004 to 2008.Snow cover has been monitored using Advanced WiFS data of RESOURCESAT-I. The sensor is suitable due to high temporal frequency of 5-day intervals, better radiometric resolution and detection of snow under shadow has facilitated monitoring of snow in Sikkim Himalayas.