The mating behavior of ring-tailed lemurs at Berenty, Madagascar, was observed in April 1982. Although Troop A included five adult females, only two were observed to mate. The mating period covered two consecutive days, April 24 and 25. Each female was receptive for about 4 hr. Data from 47 copulations, of which 38 were with ejaculation, suggest that to be the first mating partner is of importance for male ring-tailed lemurs. Previously it has been suggested that male dominance is of little significance in determining mating partners. In this investigation it was observed that the second most dominant male MK was always the first mating partner. Only after several ejaculations and resultant fatigue did he lose possession of the female to lower ranking males, and the first ranking male was not seen to copulate with either female at any time. These results suggest that a male's mating success is partly, but not completely correlated with his dominance rank, and that other factors, including his length of residence in the group and female choice, also determine patterns of mating.