More than 500 male-male interactions were recorded in a population of 560 fallow deer in order to evaluate the importance of fight duration as an index of risk and benefit. Fight duration was affected by rank, presence or absence of parallel walk in the fight sequence and, to a lesser extent, presence of females. Higher-ranking bucks fought for longer than low-ranking ones, probably because parallel walks were more common during fights among high-ranking than lowranking bucks. The high level of competition in this population may explain why fights were shorter in the presence of does, which can be considered a shortterm resource: fighting for too long could mean a lost mating opportunity.