The oxygen isotopic composition of the winter precipitation was observed in Tohkamachi, central Japan, in 1993/1994 and 1994/1995 winter. Synoptic meteorological conditions of winter precipitation in this area are classified as winter monsoons, cyclones positioned over the Sea of Japan, and cyclones located over the Pacific Ocean near Honshu (main Japanese Island). The oxygen isotopic composition of precipitation does not correlate with surface air temperature (r=0.012). A close relationship is instead observed between temperature at the cloud top and the oxygen isotopic composition of precipitation (r=0.662), and the mutual relationships are recognized for each weather condition formed under that winter precipitation (r=0.772 for winter monsoon, 0.935 for cyclone positioned over the Pacific Ocean near Honshu). Winter precipitation formed during the winter monsoon has a higher value of oxygen isotopic composition than those formed when a cyclone is positioned over the Pacific Ocean near Honshu at the same temperature. ¿ 2001 American Geophysical Union