The physiological mechanisms and acoustic principles underlying sound production in primates are important for analyzing and synthesizing primate vocalizations, for determining the range of calls that are physically producible, and for understanding primate communication in the broader comparative context of what is known about communication in other vertebrates. In this paper we discuss what is known about vocal production in nonhuman primates, relying heavily on models from speech and musical acoustics. We first describe the role of the lungs and larynx in generating the sound source, and then discuss the effects of the supralaryngeal vocal tract in modifying this source. We conclude that more research is needed to resolve several important questions about the acoustics of primate calls, including the nature of the vocal tract's contribution to call production. Nonetheless, enough is known to explore the implications of call acoustics for the evolution of primate communication. In particular, we discuss how anatomy and physiology may provide constraints resulting in “honest” acoustic indicators of body size. © 1995 Wiley-Liss, Inc.