Like many parts of India, Assam is well known as the land of varied castes and tribes since times immemorial. The people and their mode of life in different periods of history moulded varied social, cultural and economic traits in Assam. The social, cultural and economic landscape of the state is very much unique with assimilation and association of different community. People of the Scheduled Tribes and Scheduled Castes are more interested in maintaining social peace and harmony in Assam. There exists a very significant difference regarding demographic and socio-economic patterns of Scheduled Tribes and Scheduled Castes people with those in other parts of the country. The present study is an attempt to discuss about the different socio-economic aspects and demographic patterns of Scheduled Tribes and Scheduled Castes with particular reference to Sivasagar district of Assam.