This chapter develops an expanded adaptation of Hockett's design features of language, to compare the purely-vocal communication of humans and free-ranging chimpanzees. The hypothesis is that a chimpanzee type of vocal communication system provides an important preadaptation that could have facilitated the origin of human language. This preadaptation consists of a complex and varied repertory of vocal communication signals, the product of a well-bonded territorial community that is subject to constant internal fission and fusion. Because individuals are contimually changing subgroups, this species appears to have a greater variety of reasons to communicate, when out of sight, than does any other nonhuman primate.As a result, chimpanzees must communicate at a distance frequently and in many different comtexts through the vocal channel alone, without the benefit of the nonvocal communication upon which all primates rely so heavily. The direction taken by human language was to develop the vocal channel of communication far more extensively than the nonvocal channel, so this behavior of wild chimpanzees may be viewed as an important first step in the same direction.Comparison with humans demonstrates that chimpanzee vocal communication exhibits at least significant rudimentary tendencies with respect to the great majority of Hockett's design features. There remains the crucial issue of voluntary control over the vocal apparatus, even though for certain calls it has been demonstrated that wild chimpanzees appear to have significant flexibility in this area. Because such flexibility constitutes an important preadaptation, suggestions are made for experiments, carefully designed to be congenial to chimpanzee vocalization abilities, that might enable captives to master a vocal as opposed to a manual artificial language. It is proposed that such experiments would enable researchers to determine much more precisely the degree to which voluntary control exists in chimpanzee vocal functioning.