The explanation of the peculiar shape and motion of the laser-induced air spark given by Ramsden and Savic (1964) implies that at the end of the laser pulse heated air fills a spherical sector bounded by the focused laser beam. This air volume expands and forms a blast wave with perturbed spherical symmetry. In this paper, the motion of this wave is considered theoretically and the results are compared with recent interferometric measurements by Alcock, Panarella, and Ramsden (1965).