The papers in this volume were presented at "Computing: the 4th Australasian Theory Symposium", held 2-3 February 1998 at the University of Western Australia, Perth. The symposium brought together researchers in theoretical computer science throughout the Australasian region as well as Greece, Germany, Sweden, UK and USA. Of the 41 papers received, 20 were finally selected, rendering this publication a top-class review of the most recent work being done in Theory of Computation.