Abstract. The local classification of real hypersurfaces in a compact rank one symmetric space has been investigated by many people. Making use of the global behavior of geodesics on CROSS, we prove that a complete real hypersurface in a CROSS is a metric sphere if its shape operator and the curvature transformation with respect to the normal have the same eigenspaces at each point of it and if its principal curvatures are constant. We emphasize that our discussion is independent of the choice of the coefficient fields of projective spaces with constant holomorphic sectional curvature.