The statistical characteristics of compressional Pc 5 waves are studied using magnetic field data obtained by GEOS 2 and 3 geosynchronous satellites during 2-year period of August 1978 to August 1980. Depending on the second-harmonic component in the compressional component of the magnetic field oscillation, the compressional Pc 5 waves are classified into the three types: the harmonic, transitional and normal types. It is found that the harmonic and transitional types have significant azimuthal perturbations and show right-handed polarization with respect to the local magnetic field. The occurrence of these types is limited to the region close to the effective equator in local time sector of 1500~1700 LT, associated with a depression in the local feild magnitude during geomagnetically active periods. Most of the normal type have small amplitude in the azimuthal component. However, when the normal type (corresponding to compressional Pc 5 waves examined in previous works) has a large azimuthal perturbation, it shows the left-handed polarization. We try to find relating results to the excitation mechanisms developed in the past few years. Especially, we focus on the polarization properties of transverse perturbation which may reflect the spatial inhomogeneity of the media through the finite amplitude effect. It is suggested that the polarization of the transverse perturbation of compressional Pc 5 waves arises from that of the Alfv¿n mode. ¿ American Geophysical Union 1988