A stroboscopic pulse radiolysis system is described which detects the transient absorption generated by a 20 psec pulse from a 20 MeV linear accelerator. The time resolution is obtained by using, as the analyzing light, the short pulse of ?erenkov light generated by the portion of the electron beam which passes through xenon. The remaining portion of the electron beam is delayed by passing around a 270° magnet and the delay of the light may be varied by an optical delay line. Block diagrams for the electronics and the optics are given. The magnitude of sources of errors are discussed.