An experimental investigation of steady-state natural convection heat transfer was carried out in finite rectangular air layers heated from above. Two different aspect ratios, namely A = 20 and 80, and perfectly conducting boundary conditions on the end walls were used. The angle of inclination was varied from phi = 0 (heated from below) to phi = 180 degrees (heated from above). A total of 226 test points were taken for heat transfer measurements in air layers healed from above at four different orientations in the range 120 less than or equal to phi less than or equal to 180 degrees for Rayleigh numbers between 10(2) and 2x10(6). Additional test points have been carried out to show the effect of the angle of tilt in the range 0 less than or equal to phi less than or equal to 180 degrees on the average Nusselt number for fixed values of the Rayleigh number. Local measurements of the Nusselt number over discrete portions of the air layer are reported to show the Nusselt number distribution over different flow regimes.