This paper describes experimental results on thermal behavior in sealed natural air-cooled electronic equipment casing. One of the authors has already proposed a simple practical equation for thermal design of a sealed natural convection air-cooled electronic equipment casing. However in that study the casing was made of plastic and had a cube shape of side length of 0.4m. Therefore, in the present work, an aluminium casing having length, width and height of 0.1m, 0.4m, and 0.3m, respectively, was used. The temperature of casing surfaces and air inside the casing were measured with various inclinations and for three different ways of casing setting on the floor. Results indicated only a small change in value of the coefficients used in the equation developed by one of the author.