Eclogites in metamorphic complexes of the USSR are of different types with regard to their tectonic conditions and compositions. They are: 1) tectonic inclusions in serpentinite melanges; 2) members of eclogite-glaucophane schist complexes; 3) inclusions in blastomylonite zones; and 4) those within gneiss complexes. Based upon the study of their relationships with country rocks, chemical zoning of coexisting garnets and omphacites, and compositions of gaseous-liquid inclusions in minerals, a polygene character of the eclogites has been shown. P-T equilibrium parameters for eclogites associated with glaucophane schists are commonly close to those of the latter. Eclogites of gneiss complexes tend to be characterized by variable conditions of formation, even within a single complex.