In the lobe/mantle region at ~159 RE away from the Earth during a geomagnetically disturbed period, we have found the coexistence of three ion species, H+, He++, and O+, streaming tailward with nearly the same flow velocity ~200--500 km/s. Both H+ and O+ ions are detected almost continuously from near plasma sheet to near magnetopause region. From a positive correlation between the proton density and their velocity component parallel to the magnetic field VH+∥, we conclude that most of protons have come from the solar wind. The existence of He++ further supports this conclusion, which implies the importance of solar wind contribution to the magnetotail. The existence of O+, on the other hand, suggests that the ions of ionospheric origin have mixed with those of solar wind origin. The lack of positive correlation between O+ density and VO+∥ is consistent with the idea that O+ ions have some source mechanism different from that of protons. Simultaneously, curious velocity differences are also observed: VO+∥ appears to be often faster than VH+∥ by ΔV∥=20--30 km/s. This observation may provide a key for further discussion. ¿ American Geophysical Union 1996