The thermal field and the heat transfer characteristics of a system consisting of two staggered vertical plates cooled by air in free convection were experimentally studied. The parameters investigated included the interplate spacing, the magnitude of the vertical stagger, and the Rayleigh number based on the overall convective heat flux From each plate. The experiments were performed in air. The schlieren optical technique was employed to obtain the thermal field around the plates and the local heat transfer coefficients along the vertical sides of plates. Staggering was found to markedly affect the local heat transfer characteristics of the facing sides of the plates when the interplate distance was relatively small. In general, the Nusselt number averaged on the inner face of the lower plate was enhanced (up to over 40%) compared with that for the case of the unstaggered plate channel. Conversely the mean Nusselt number on the facing side of the upper plate was reduced (up to 15%).