A building that is equipped with a natural ventilation system gives greater physical comfort for its occupants and saves on electricity consumption. The flow structure of fluid-driven natural cross-ventilation is studied using three techniques: flow visualization, Particle Image Velocimetry (PIV) measurement and Computational Fluid Dynamics (CFD). Four specific cases are chosen to study the effect of the number of windows and the window configuration on cross-ventilation performance. A comparative discussion of these cases is provided and the significant advantages and disadvantages for each case, with regard to ventilation, are reported. There is satisfactory agreement between the results obtained from computation and those from the experiment, which provides an effective guideline for CFD users for the validation of future numerical approaches. A novel numerical technique is used to provide an insight into the quantification of the movement of entering air. The three dimensionality, turbulence and the replacement of the indoor fluid are visualized. The overall performance is significantly affected by the specific design of the cross-ventilation system. It is found that a larger volumetric flow rate does not always ensure better replacement of the indoor air, and vice versa. (C) 2013 Elsevier B.V. All rights reserved.