Heat transfer due to all participating modes has been measured for a heated horizontal cylinder in the presence of adjacent adiabatic walls which partially enclose the space in which the cylinder is situated. The three investigated configurations included a vertical wall situated to the side of the cylinder, a horizontal wall beneath the cylinder, and a corner formed by the intersection of the vertical and horizontal walls. The separation distance between the cylinder and the wall(s) was varied parametrically, with the closest spacing between the cylinder periphery and the wall(s) being 1 12 cylinder diameter. In the main body of experiments, the surfaces of both the cylinder and the wall(s) were of high emissivity. In general, the wall-cylinder interactions tended to reduce the cylinder heat transfer, with greater reductions at closer spacings. In the presence of a side wall, the largest measured reductions were about 20%; at spacings of 1 4 diameter and greater, the reductions were negligible. A bottom wall (without a side wall) caused reductions about 5% greater than those due to the side wall, while the corner-cylinder interactions brought about significantly greater reductions (as much as 40%). Supplementary experiments performed with a low emissivity cylinder demonstrated that radiation effects played a substantial role in the wall-related reductions in cylinder heat transfer.