In this study, an inverse radiation analysis is presented for the estimation of the radiation properties for an absorbing, emitting, and scattering media with diffusely emitting and reflecting opaque boundaries. The repulsive particle swarm optimization (RPSO) algorithm, which is a relatively recent heuristic search method, is proposed as an effective method for improving the search efficiency for unknown radiative parameters. To verify the performance of the RPSO algorithm, it is compared with a basic particle swarm optimization (PSO) algorithm and a hybrid genetic algorithm (HGA) for the inverse radiation problem in estimating the various radiation properties in a two-dimensional irregular medium, when the temperatures are given at only four measurement positions. A finite-volume method is applied to solve the radiative transfer equation of a direct problem to obtain measured temperatures. RPSO is proven to be quite a robust tool for simultaneous estimation of multi-parameters even in a strongly-coupled environment. (c) 2007 Elsevier Ltd. All rights reserved.