The aims of our follow up observational study were to clarify the transition from pre-linguistic com-munication to early language and to show how dependent the development of verbal behaviour was upon the nature of the interaction taking place between mother and child from the early months. Over a 22-month period fortnightly observations were made of 8 mothers and their firstborn children (2-23 months old) as they interacted at home, in natural and in semistructured situations. Maternal and child behaviours were recorded by time-sampling method on the observation checklist consisting of 40 maternal and 65 child categories of behaviour. In the present paper, part of this comprehensive sampling was analyzed in terms of (a) frequency of child vocalizations (FIG. 1), gaze (FIG. 2) and facial or gestural communications (FIG. 3),(b) co-occurr-ence of maternal or child categories of behaviour with child vocalizations, i. e. crying, negative vocalization (TABLE 3), babbling (TABLE 4), pre-speech and speech (TABLE 5). It was demonstrated that child speech exhibited after 16 months of age, turntaking (alternation) with his mother; whereas it was only at the age of 22-23 months that pre-speech being also an intentional vocalization, exhibited alternation pattern instead of previous coaction pattern. As for babbling, it revealed that it had two functions, i. e. play by oneself and expression of pleasure. The latter exhibited coaction pattern at 2-5 months of age, and the alternation pattern occured after 6 months. On the other hand, crying and negative vocalization exhibited only coaction pattern (2-19 months).