Active chilled beam systems, which have been gaining much popularity recently in Europe and North America, are known to be not only energy-efficient but also advantageous to uniform indoor environment quality. The objective of this study is to evaluate the performance of an active chilled beam system, in terms of air diffusion and local discomfort in the conditioned room. To do this, the evaluation was conducted using a full-scale test bed, where an active chilled beam system is designed and operated with a dedicated outdoor air system. A 2-axis traverse system was utilized to measure the air temperature and air velocity in the entire space of the test bed. The performance was evaluated using the three indices: ADPI to evaluate the uniform thermal comfort, DR(draught rate) to evaluate the discomfort due to excessive air movement, and vertical air temperature difference to evaluate local discomfort due to thermal stratification. The result shows that active chilled beam system is successful in providing the uniform indoor thermal environment with less supply air flow rate.