This book constitutes the refereed proceedings of the 4th International Workshop on Next Generation Information Technology and Systems, NGITS'99, held in Zikhron-Yaakov, Israel in July 1999. The 17 revised full papers presented were carefully reviewed and selected from 34 submissions. Also included are five reviewed short papers and abstracts of two invited talks. The papers are organized in topical sections on exploring the World Wide Web; database technology; storage, meta-information, ontologies, and software engineering; agents and work flow management technology; and data warehousing and mining.