This paper presents numerical simulation of wind field and contaminant dispersion in the flow over a group of buildings by large eddy simulation (LES) with higher accuracy finite volume method (FVM) for numerical discretization of governing equation and with immersed boundary method (IBM) at building surfaces. The paper is aimed at proposing a numerical method which can deal with the complex turbulent flow and contaminant dispersion inside a group of buildings. The geometry of the building layout and flow parameters are taken from the wind tunnel experiments by Davidson et al. [1996. Wind tunnel simulations of plume dispersion through groups of obstacles. Atmospheric Environment 30 (22), 3715-3731] so that the feasibility and reliability of the numerical method and code can be examined by comparison between numerical results and experimental measurements with confidence. The flow patterns and contaminant dispersion inside the group of buildings are shown in agreement with the description of Davidson et al. [1996. Wind tunnel simulations of plume dispersion through groups of obstacles. Atmospheric Environment 30 (22), 3715-3731]. The numerical prediction of the statistical properties of contaminant dispersion, e.g. the mean concentration distributions, lateral and vertical spreads of the contaminant an so forth, is in good agreement with wind tunnel experiment measurements. The numerical study of this testing case reveals a number of issues which should be considered in application of LES to such complex turbulent flows in environment engineering, e.g. spatial resolution, reasonable subgrid stress model and the turbulent intensity in atmospheric boundary layer. © 2007 Elsevier Ltd. All rights reserved.