The hypothesis that territoriality of female meadow voles (Microtus pennsylvanicus) regulates population size was tested during four breeding seasons by using radiotelemetry to determine home range, dispersion, and use of vegetative cover in crownvetch (Coronilla varia) fields. The percentage of transient voles in the population was related directly to density. The percentage of transient females increased as nearest-neighbor distances between females decreased. Territory size for females was related inversely to available forage, supporting the hypothesis that territory size is a function of availability of food. I conclude that the quantity of forage is a factor in controlling population density.