Hand preferences for a coordinated bimanual task were assessed in a sample of 31 captive gorillas (Gorilla gorilla) and 19 captive orangutans (Pongo pygmaeus) and were compared with chimpanzee (Pan troglodytes) hand preferences in subjects that were matched on the basis of age, sex, and rearing history. The task required that the apes remove food from the inside edges of a symmetrical polyvinyl chloride pipe presented to them in their home cages. The results indicate significant species differences with chimpanzees showing population-level right-handedness and orangutans showing population-level left-handedness. The gorillas showed a nonsignificant trend toward righthandedness. The results are discussed in terms of possible ecological or biomechanical factors that may influence hand preferences in different ape species.The evolution of handedness has been a topic of historical (Warren, 1980) and contemporary debate (Fagot & Vauclair, 1991;Hopkins, 1996Hopkins, ,1999MacNeilage, Studdert-Kennedy, & Lindblom, 1987;Marchant & McGrew, 1991;McGrew & Marchant, 1997). The central issues surrounding evolutionary theories of handedness have focused on whether population-level right-handedness is a uniquely human adaptation and whether the mechanisms selecting for handedness are associated with the emergence of complex cognitive processes such as language or tool use (see Bradshaw & Rogers, 1993, for a review). Since the seminal review article on nonhuman primate handedness by MacNeilage et al. (1987), there have been a plethora of studies on the distribution of limb and hand preference in a variety of animal species, notably nonhuman primates. Although there continues to be considerable debate over whether population-level handedness is expressed in nonhuman primates, evidence has emerged for several measures suggesting population-level handedness in limb preferences in a variety of vertebrates (for reviews, see Bradshaw & Rogers, 1993;Hook-Costigan & Rogers, 1997;Rogers & Andrews, 2002;Ward & Hopkins, 1993 One difficulty with the interpretation of findings on handedness between species has been the lack of common measures of hand use. The most commonly used measure of hand preference is simple reaching, and many primate species have been tested for handedness using this task (see Lehman, 1993). For simple reaching, some have reported increasing preferential use of the right hand for nonhuman primate species more closely related to humans than for species more distantly related (see Westergaard, Kuhn, & Suomi, 1998, for a review), whereas others have not reported such effects (see Hopkins & Morris, 1993;McGrew & Marchant, 1997). Direct comparative studies of simple reaching in great apes that have used the same measures and testing procedures have revealed mixed results with some authors reporting populationlevel right-handedness (Olson, Ellis, & Nadler, 1990) and others not (Heestand, 1986). However, simple reaching is not a particularly complex motor task and is not the most sensitive measure of hand preference ...