The period immediately following birth appears to be particularly well suited to study the developmental similarities in vocal communication between man and other primates. Vocalisations performed by non-human primates during their first year of life are therefore particularly important in a comparative and evolutionary perspective, as they allow interesting comparisons with studies on human linguistic development. However, this topic has received little attention. We studied the functional relationships, in a social colony of pig-tailed macaques Macaca nemestrina, between the maternal response to the search for physical contact by the young and the physical structure of the vocalisations produced by the latter. The research was performed on three mother-young dyads, audio-recording the vocalisations produced by the young and by the adults and video-recording mother-young interactions. Our results provide a description of some of the physical characteristics of the vocalisations produced by the young during spontaneous interactions with their mothers; furthermore they suggest the existence of different structural or syntactical categories and suggest a relationship between maternal behaviour and vocalisation patterns.