This book constitutes the thoroughly refereed post-proceedings of the 4th International Workshop on Mining Web Data, WEBKDD 2002, held in Edmonton, Canada, in July 2002.The 10 revised full papers presented together with a detailed preface went through two rounds of reviewing and improvement and were selected from 23 submissions. The papers are organized in topical sections on categorization of users and usage, prediction and recommendation, and evaluation of algorithms.