Section 1 formalizes the notion of a replicated database and presents the basic techniques for achieving consistency. Section 2 describes a technique for deleting items from the database; deletions are more complicated than other changes because the deleted item must be represented by a surrogate until the news of the deletion has spread to all the sites. Section 3 presents simulation and analytical results for non-uniform spatial distributions in the choice of anti-entropy and rumor-mongering partners.