PostgreSQL is an open-source relational database management system (RDBMS) that dates back to the Ingres project at the University of California at Berkeley in the 1970's. In the 1980's, object-oriented features were added and in the 1990's SQL was added (resulting in the current name). Given this history, PostgreSQL is clearly a mature product that has undergone extensive development. An enthusiastic and active user group continues to refine PostgreSQL and among the significant recent developments has been a native Windows operating system port. PostgreSQL has been called the most advanced open-source RDBMS available and a review of its features shows this appellation is deserved. Documentation is excellent and additional reference books are available. It is entirely free for personal and commercial use.