A method for determining the evolution of spark channels, reported by Creagh, Fletcher and Somerville, has been used to determine the evolution of the conducting channel formed when an approximately 30 A spark occurs in oxygen at pressures of 411, 680 and 985 torr. The channel expands for approximately 100 nsec in close association with a cylindrical shock wave. A period of slower expansion follows in which, presumably, conditions within the channel approach pressure equilibrium. The column then cools and contracts by a process of radial thermal conduction. The theory of channel decay proposed by Creagh et al. has been used in the analysis of the decay of these channels and a satisfactory agreement with experiment has been found.