The transient thermal responses in a two-dimensional semitransparent cylinder with black boundary surfaces caused by a pulse irradiation at one end of the cylinder are studied. The processes of the transient coupled radiative-conductive heat transfer in the cylinder are analyzed numerically. An implicit central-difference scheme is employed for handling the energy equation, while a discrete-ordinates method is used to solve the radiative transfer equation. The effects of various parameters on the transient thermal responses are investigated. It is found that, due to the radiation within medium, the transient temperature of the nonirradiated end surface of the cylinder can be greater than that of the inner medium of cylinder. Temperature evolution curves with two peaks can be observed under some conditions at the nonirradiated end of the cylinder. The effects of the conduction-radiation parameter, the optical thickness and refractive index on the transient temperature responses are large. The effects of single-scattering albedo are more significant for the radiation-dominated case than that for the conduction-dominated case.