Transient response of a planar participating medium subjected to a short-pulse diffuse or collimated radiation is investigated. The pulse-width of the radiation is of the order of a nano-second. Short-pulse radiation can have a step or a Gaussian temporal variation. The homogenous participating medium with diffuse-gray boundaries is absorbing and scattering. The north boundary of the participating medium can be under the influence of a pulse train consisting of 1-4 pulses. The analysis is done using the finite volume method. Effects of the extinction coefficient and the scattering albedo on transmittance and reflectance signals are studied for a train of pulses. Unlike the previous studies with a single-pulse, a train of pulses provides more useful information about the medium. (C) 2007 Elsevier Ltd. All rights reserved.