The present work gives an overview of the existing knowledge on radiative transfer in packed and fluidized beds. Special emphasis is given to the proper usage and determination of radiation characteristics of the particles in these systems. Models that treat the particulate bed as a continuum are discussed along with those that consider the system as discontinuous, i.e., accounting for the phase boundaries between the gas and the particles. Existing experimental techniques for determining the radiative properties are presented, and the published bed transmittance and reflectance data are discussed and compared with the theoretical predictions. Interaction of radiation with other modes of heat transfer is also examined.