Tourism is a major activity in the Greek islands. Its development during recent decades has stopped the economic and demographic decline of the area. The paper develops a framework for the appraisal of tourism's sustainability in the Greek islands, and it is concluded that the conventional tourist model, based on sun, sea and sand (3S) has failed to promote sustainability due to the limited economic benefits for host communities and growing environmental pressures. The latest trend in Greece and elsewhere is a shift from mass tourism to more environmentally friendly and sustainable forms of tourism. Policies to change tourism patterns in the Greek islands will need to take into consideration their unique characteristics, their existing realities, and to be based on the exploitation of the local natural and cultural resources in order to develop new forms of tourism. The purpose of this paper is to identify types of new forms of tourism that are being developed in the Aegean Islands, and to evaluate their impact. Various practical examples are presented, together with the difficulties involved in their implementation. The initiatives are in fact so recent that it is difficult to assess their tangible results.