Abstract: Petrographic and microtextural features of the metamorphic rocks cropped out in the Marmara Island indicate that they have three identifiable metamorphic phases (Mj, M2, M}). The first two phases (Mj, M2) form the parts of a single progressive regional metamorphic cycle. The last phase (M3) represents the retrograde metamorphism. Typical mineralogical changes in the metamorphics delineate that the degree of metamorphism increases from north to south. Based on these mineralogical changes, three metamorphic fades zones have been distinguished. These are greenschist, epidote-amphibolite and amphibolite fades. These fadeszones generally run parallel to the trend of the D2fold axis in the ENE-WSW direction. By determining the formational conditions ofindex minerals, it is found out that the progressive regional metamorphism occurred beneath a magmatic arc at pressures between 3and 6 kbar and temperatures between 400 and 600°C. Under these conditions, the rocks have undergone four phases of deformation,synchronous with the regional metamorphism.