This paper presents the results of an interferometric study of the convective heat transfers across enclosed, vertical, high aspect ratio, air-filled rectangular cavities fitted with baffles. These inserts were mounted vertically from the top and bottom spacers which were used to separate the hot and relatively cold plane walls of the system. Both solid and porous gauze baffles were employed. The effects of baffle type, size and placement, on both the local and average free convective heat transfers, are discussed. Reference is also made to supplementary flow visualisation studies.