An explanation, based on a statistical model, of the pulse breakdown of liquid argon is reported. The electric strength is strongly dependent on cathode oxidation and the results indicate that positive ions play an important role in the breakdown process. From a series of time lag measurements the formative time to breakdown appears to be about 0.1 μsec while statistical lags greater than 20 μsec have been observed at electric stresses above 1.7 MV cm^-1. In general, the behaviour of liquid argon under pulse voltages is similar to that found previously for hydrocarbons.