The purpose of this study is primarily to analyse empirically the productivity effects of worker participation in capital by Korean employee stock ownership plan that had taken newly effect on and after January 1,2002, and secondarily to examine the impact of unionization on productivity. The analysis data are those of 150 firms that listed or registered on the stock market, and introduced ESOP. The result of this study can be summarized as follows. First, the worker participation in capitia have significantly a positive effect on productivity, but the magnitude of those effects vary according to estimation models and sectors. The elasticity of stock share owned by employees on productivity is from 0.03 to 0.24. Second, there is no unitary relationship between unionization and productivity. The coefficients of union dummy variable are positive or negative according to models and sectors as well as insignificant.