Numerical studies were performed on natural convection heat transfer from radial heat sinks with perforated ring. The effects of perforation number (0-6), perforation diameter (0-3 mm), and perforation length (1.5-6 mm), and orientations angle (0-180 degrees) on the thermal performance were investigated. The results show that radial heat sinks with a perforated ring obviously have better thermal performance than that with imperforated ring. Upwardly oriented radial heat sinks have the best thermal performance while sideward oriented radial heat sinks yield worst thermal performance. The geometric parameters of perforation is shown to affect the thermal performance of heat sink significantly at relatively higher heat transfer rate, especially for upward and sideward orientations. The thermal resistance of the radial heat sink with optimized perforated ring was shown to be less than that of imperforated ring by 17%, while reducing the mass of ring by up to 37%. This can be attributed to the unhindered natural convective flow through the perforation. (C) 2016 Elsevier Ltd. All rights reserved.