Ultrahigh-pressure (UHP) metamorphic rocks, represented by coesite- or its pseudomorph-bearing eclogites, have been found mainly from continent-continent collision orogenic belts, and garnet peridotite bodies are also known to occur in such UHP belts. The UHP eclogites and garnet peridotite bodies/layers/lenses are commonly enclosed within metamorphic rocks derived from continent crustal materials composed by moderate to low pressure metamorphic minerals, although they should have been located under deep mantle depths (&gt
50km). Therefore, elucidation of juxtaposition processes between the mantle material and the host crustal material is one of main subjects for the petrology in the UHP belts. Delineating of pressure-temperature (P-T) paths of these UHP garnet peridotite bodies can give us indispensable constraints to clarify the juxtaposition process of mantle and crustal materials in the continent-collision settings and the exhumation processes of deeply subducted rocks with higher density than the crustal rocks. In this paper, we summarize the commonly used methods to determine P-T histories of the UHP garnet peridotite bodies (i.e., geo-thermometer and barometer) and discuss P-T paths of UHP rocks in collision type orogenic belts, and their tectonic significance. © 2012, Japan Association of Mineralogical Sciences. All rights reserved.