Transient individual liquid slug motion in a voided line is investigated both numerically and experimentally. In a series of experiments, slugs of various lengths are propelled into an empty pipe under varying air pressures controlled at an upstream reservoir. The pressure-time histories created by the impacting slugs at an elbow located at the end of the pipe reach are measured, and the peak pressures are in reasonable agreement with results reported in an earlier study. An analytical model is developed to predict the slug acceleration and its impulse at the elbow. Comparisons between measured and predicted parameters reveal the random nature of the slug motion and subsequent impact. (C) 1997 Academic Press Limited.