1607 OH/IR stars associated with IRAS sources are assembled and the IRAS LRS spectra of 980 OH/IR stars are examined in this paper. The nature of the circumstellar dust for these sources is classified. The distributions of these subgroups of OH/IR stars in the IRAS color-color diagram and the period-color diagram are interpreted with their evolutionary status. The Galactic and the velocity distributions of these subgroups of OH/IR stars are also presented. The correlations among the expanding velocities of the envelopes, colors, periods and the pumping efficiencies for subgroups of OH/IR stars are investigated to outline the evolutionary status of OH/IR stars.

• P. S. CHEN(Department of Physics & Astronomy, University of Calgary/Yunnan Observatory & Joint Laboratory for Optical Astronomy, Chinise Academy of Science)
• S. KWOK(Department of Physics & Astronomy, University of Calgary)