The past literature describing the possible sites of the sound-producing mechanisms in delphinid cetaceans is reviewed. The morphology of the nasal sac system of delphinids which has been implicated in the production of sounds, by most investigations, is discussed with special emphasis placed on the physical characteristics of these sounds. New data on the histological structure of the epithelia throughout the nasal region of a delphinid are presented with some suggestions as to its function. The presence and structure of glandular tissues are described along with a discussion of their potential role in the production of sound. It is concluded that the theories implicating the nasal sac systems of odontocete cetaceans in the production of sound are additionally supported by certain anatomical specializations adjacent to the tissues of this system.