An effective thermoelectric material requires good electrical conductivity, high Seebeck coefficient but low thermal conductivity. In this paper, we summarize some of our works on the thermoelectric properties of beta-Zn4Sb3 in both bulk and thin film forms showing their relationships with doping, microstructure and phase constitution. Although no significant improvement can be achieved in the hot-pressed beta-Zn4Sb3 based materials by In-doping and/or microstructure adjustment, a high ZT of 1.2 at 460K can be achieved in the Zn4Sb3 thin films prepared by magnetron sputtering. This is largely due to the properly controlled thickness and microstructure in the thin films which are highly different from that of their bulk counterpart.