Directories have become an important component of the enterprise security and identity management middleware. This paper describes a novel filter based replication model for Lightweight Directory Access Protocol (LDAP) directories. Instead of replicating entire subtrees from a Directory Information Tree (DIT), only entries matching a filter specification are replicated. Efficient algorithms for selecting such filters, keeping them synchronized with the master copy and for using them to answer directory queries have been proposed. Advantages of the filter based replication framework over existing subtree based mechanisms have been demonstrated for a real enterprise directory using real workloads.