This book constitutes the thoroughly refereed joint postproceedings of the 4th International Workshop on Knowledge Discovery in Inductive Databases, KDID 2005, held in Porto, Portugal in October 2005 in association with ECML/PKDD.

The 20 revised full papers presented together with 2 invited papers were carefully selected during two rounds of reviewing and improvement for inclusion in the book. Bringing together the fields of databases, machine learning, and data mining the papers address various current topics in knowledge discovery and data mining in the framework of inductive databases such as constraint-based mining, database technology and inductive querying.