Examination of extensive data from field and laboratory studies indicates that prairie voles (Microtus ochrogaster) are socially monogamous and form pair-bonds. We used grid-trapping data from replicate populations of prairie voles living in 0.1-ha small mammal enclosures at 2 different initial densities to examine the extent to which opposite-sex adults captured together in the same live trap reflected social associations established from nest-use patterns and the probability that the pair produced offspring. Females classified as a resident at a nest that also included at least 1 resident male (male–female pairs or groups) were significantly more likely to be trapped with a male from the same social unit (64%) rather than a male from another social unit or a male wanderer (an animal not considered a resident at any nest site). On the other hand, females residing at a nest with no resident males were caught with wandering males significantly more often (84%) than with resident males from another nest. Finally, female wanderers were significantly more likely to be trapped with male wanderers (75%) than with resident males. A genetic analysis of parentage revealed that females were significantly more likely to have produced offspring with the male with which they were caught most frequently (80% of females) than to not breed with these males. None of these findings were influenced by density. Overall, the multiple-capture data were consistent with social monogamy and the relative frequency of male–female multiple captures were predictive of the likelihood of mating. However, although most females residing at nests with resident males bred with these males (84%), a similar percentage of these females also bred with at least 1 male that never resided in the same social unit as the female, suggesting that prairie voles are not genetically monogamous throughout their lives.