This book constitutes the thoroughly refereed post-workshop proceedings of the Third International Workshop on Implementing Automata, WIA'98, held in Rouen, France, in September 1998. The 21 revised full papers presented were carefully selected from the workshop contributions after several rounds of reviewing. The papers are devoted to issues of implementing automata of various types important for areas such as parsing, computational linguistics, speech recognition, text searching, device controlers, distributed systems, and protocol analysis.