The radiation intensity at a given distance depends mainly on the radiative power and the flame's size and shape. Considerable literature describing both experimental and theoretical studies of thermal radiation from flames is available. Even so, predicting the radiant power of large flames is still subject to considerable uncertainty, because some parameters associated with large turbulent diffusion flames cannot be determined accurately for a given fire. A series of outdoor large pool-fire experiments were performed using gasoline and diesel fuels lying above a layer of water. Five concentric circular pools made of reinforced concrete (1.5, 3, 4, 5, and 6 m in diameter) were used. The experiments were filmed with at least two video cameras registering visible light (VHS) and a thermographic camera (IR). In this study, thermographic images were used to determine the flames' distribution of emissive power, the mean emissive power, and the flame's irradiance. The contribution of each part of the flame to the total radiated energy was analyzed. A method is presented combining the IR images and the visible images; it offers further insight into the relationship between the heat emitted by the luminous part and the obscured, nonluminous, part of the flame. (C) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.