Incomplete observations of matings and uncertainty about which male's sperm is responsible for fertilization have traditionally made paternity difficult to document in field research. Modern genetic methods, combined with field data, now facilitate assigning paternity in many species. I investigated male reproductive success in white-tailed deer (Odocoileus virginanus) by a microsatellite paternity analysis, which revealed that males from all age classes >0.5 years fathered offspring. The oldest males did not monopolize matings; for 12 of 14 males ≥3 years old who fathered young, the numbers of females mated and young fathered were highly variable (1–7 and 1–9, respectively). Three yearling males that bred mated with 3 yearling females and one 2.5-year-old female, whereas all other male age classes mated with females from any age class. In addition, the 1st cases of frequent multiple paternity in free-ranging white-tailed deer were documented. Multiple paternity was found in 22% of twins, with paternity assigned at the 95% confidence level. Males that jointly sired twins appeared at least a year apart in age (maximum age difference, 3 years). It is proposed that older males displaced younger males tending estrous females.