This book comprises a selection of papers that were first presented at VSS98 (5th International Workshop on Variable Structure Systems) held in Sarasota, Florida. This workshop was the fifth in a series of VSS international workshops, and the first to be held in the United States. Work presented herein on theoretical developments and applications on VSS and Sliding Mode, reflects how trends have advanced beyond the original ideas that are now well documented in a number of books and research monographs. In particular, the concepts of Sliding Sector and Second Order Sliding Mode introduced in this volume, will stimulate discussions and invite further extensions. Also, the focus on Sampled Data systems represents a positive trend towards practical industrial implementations of sliding mode controllers.