Composition of the diet of fallow deer in the New Forest in southern England was determined on a monthly basis from faecal analyses. The deer were shown to be predominantly grazers: grasses accounted for approximately 70% of annual forage intake, with the remainder of the diet dominated by sedges, rushes, heather and broadleaved browse. Differences in dietary composition and diet quality could be shown between males and females where buck and doe groups occupied discrete home ranges. Differences between the male and female diets were also maintained in areas where the two sexes. while still socially segregated, occupied overlapping ranges. Males had higher quality diets in winter, while females consumed higher quality diets in spring and summer. These results are considered in the context of general theories of dietary difference between the sexes in dimorphic species of ungulates.