The first recordings of single neurone activity in the auditory system were made from the cochlear nucleus of the cat, by Galambos and Davis (1943). In these experiments the authors were attempting to record from fibres in the cochlear nerve; subsequently, however, they concluded that the recordings had been from aberrant cells of the cochlear nucleus lying central to the glial margin of the VIII nerve (Galambos and Davis, 1948). The first successful recordings from fibres of the cochlear nerve were made by Tasaki (1954) in the guinea pig. These classical but necessarily limited results were greatly extended by Rose, Galambos, and Hughes (1959) in the cat cochlear nucleus and by Katsuki and co-workers (Katsuki et al., 1958, 1961, 1962) in the cat and monkey cochlear nerve. Perhaps the most significant developments have been the introduction of techniques for precise control of the acoustic stimulus and the quantitative analysis of neuronal response patterns, notably by the laboratories of Kiang (e.g. Gerstein and Kiang, 1960; Kiang et al., 1962b, 1965a, 1967) and Rose (e.g. Rose et al., 1967; Hind et al., 1967). These developments have made possible a large number of quantitative investigations of the behaviour of representative numbers of neurons at these levels of the peripheral auditory system under a wide variety of stimulus conditions.