In the last years the Global System for Mobile communication, GSM, has gained a tremendous success around the world. Meanwhile more than 250 operators offer their GSM services to over 66 Mio customers in 110 countries. Before this success could be imagined, work was started in ETSI to specify first drafts for the interworking of Digital Enhanced Cordless Telecommunications, DECT, to GSM. The extension of GSM using DECT as a complementary air interface was seen as a step towards more capacity and enhanced radio performance, using synergies and the best characteristics of both systems. During the last years different access standards for DECT were elaborated, including the DECT/GSM Interworking Profile, GIP. This profile allows the attachment of DECT to GSM, while using all specified GSM phase 2 services, like supplementary services, facsimile, bearers services and the short message service (SMS) via the DECT air-interface. The following chapters describe the access technology DECT, some of the specified access profiles, different technical DECT/GSM integration scenarios and indicates the advantages and drawbacks of the usage of DECT as an extension to GSM in the residential, business and public environment.