The energy requirements of the world are increasing day by day. Major energy requirements are met by combustion of limited fossil fuel resources. A considerable part of this energy gets rejected to the environment in the form of waste heat due to the low conversion efficiencies.Thermoelectric materials can be used to convert the waste heat into electrical energy and hence can help us in efficient utilization of the fossil fuels. Skutterudites are prominent thermoelectric material because of their high electronic and thermal properties. In this dissertation, my investigation is on the electronic and thermal properties of CoSb3 based skutterudites.CoSb3 based kutterudites are well-known material for intermediate temperature thermoelectric applications. By introducing a rattling atom in the unfilled skutterudites the thermal conductivity can be further lowered due to incoherent rattling in the structure. The choice of filler atom depends on the extent of the rattling of guest atoms. We solve the transport equations for electrons and phonons to understand the electronic properties and thermal properties of lled and unlled skutterudites. Doping is simulated using a rigid band approximation.Further improvement in the thermoelectric performance is possible by nanostructuring below the largest mean free path.