Multiple regression analysis is used to predict the mean room velocity and determine the most influencing parameters on the velocity. More than 120 experiments for four different heat source locations were carried out in a test chamber with high level mixing ventilation. The measured parameters, such as supply air momentum, room heat load, Archimedes number and local temperature ratio, were used as independent variables. These parameters are examined by two methods: a simple regression analysis incorporated into scatter matrix plots; and multiple stepwise regression analysis. It is concluded that, when a heat source is located along the jet centreline, the supply momentum influences the mean room velocity regardless of change in the plume strength. However, when the heat source is located outside the jet region, the local temperature ratio is a major parameter influencing the mean room velocity.