The results obtained from both the experimental and numerical investigations of turbulent circular air jet impingement cooling of a circular heated cylinder are presented. At the surface of the heated cylinder, a constant heat flux condition was maintained. The Reynolds number, Red, defined based on the nozzle diameter, was varied from 10,000 to 25,000. The geometric parameters such as the non-dimensional distance between the nozzle exit and the circular cylinder, hid, and the ratio of nozzle diameter to the diameter of the heated target cylinder, d/D, were investigated for the range of 4-16 and 0.11-0.25, respectively. The local Nusselt number variation along the circumferential and axial directions obtained from the experimental studies are reported. To understand the flow features and to obtain the temperature and local Nusselt number distributions over the surface of the heated cylinder, a numerical study was also performed. It was observed that the stagnation Nusselt number increases monotonically as the hid decreases and the effects of hid and d/D are significant only in the jet impinging region. Based on the experimental results, a correlation for the stagnation Nusselt number has also been developed. (C) 2013 Elsevier Ltd. All rights reserved.