Integrity constraints are a key tool for characterizing the well-formedness and semantics of the information contained in databases. In this regard, it is essential that intelligent database management systems provide their users with automatic support to effectively and efficiently maintain the semantic correctness of data with respect to the given integrity constraints. This chapter gives an overview of the field of efficient integrity checking and maintenance for relational as well as deductive databases. It covers both theoretical and practical aspects of integrity control, including integrity maintenance via active rules. New lines of research are outlined, particularly with regard to two topics where a strong impact for future developments can be expected: integrity in XML document collections and in distributed databases. Both pose a number of new and highly relevant research challenges to the database community.