Previous studies of the relationship between acorn production and Peromyscus populations have been conducted in regions with severe winter climate where winter breeding is rare. I trapped white-footed mice, Peromyscus leucopus, in a southern Piedmont oak-hickory forest during autumn and winter for four consecutive years to determine how acorn availability influences winter reproduction in P. leucopus. Acorn production in years 1 and 4 of the study was over 10 times higher than in years 2 and 3. Peromyscus leucopus density was highest in winters following large mast crops, but also increased following a low mast crop in year 3. Body weight was significantly lower during one of the poor mast years, but not the other. More than 50% of female mice were reproductively active during all four winters of the study. Thus, P. leucopus responded positively to high mast availability, but mice remained reproductively active even in poor mast years.