Microsoft's Directory Services strategy has come a long way in the past few years. Even before Active Directory, several Microsoft products utilized a directory, although most used one that was built in. Some examples include the NetMeeting ILS server and Exchange 5.5, which was the precursor to Active Directory. With the introduction of Active Directory in 1999, Microsoft finally had the first signs of a coherent Directory Services strategy. With the release of Windows Server 2003, plus a major overhaul of Microsoft Metadirectory Server and the introduction of Active Directory Application Mode, Microsoft has one of the most diverse and robust directory offerings of any of the major directory vendors in the market today. In this chapter, we will discuss Microsoft's future plans for Directory Services and cover how that plan fits in with interoperating with other directories and integrating with applications and services.