Nikko and Ashio areas of central Japan are contrasting habitats in food quality and availability for sika deer (Cervus nippon). In Nikko area, main understory is Sasa nipponica, which has high nutritive value but low height and small biomass under overgrazing. In Ashio area, main understory is Miscanthus sinensis, which has low nutritive value but high height and large biomass. Ashio herd has smaller body size and body mass in both sexes and lower pregnancy rate than those in Nikko herd. Deer densities were 22 and 147 deer/km² in Nikko and Ashio areas, respectively in winter of 1996. Owing to pest control, present density has been reduced to 13 and 20 deer/km² in Nikko and Ashio areas, respectively. Winter food in Nikko area was S. nipponica, accounted for 70% of rumen contents in usual, but this ratio fell when snow cover was deep or deer density was high. Winter food in Ashio area was M. sinensis, accounted for 80% of rumen contents, and this ratio was relatively stable despite of the changes in deer density and snow depth. These results suggest that quantity habitat in Ashio area can maintain higher carrying capacity with smaller body size than the quality habitat in Nikko area.