20 healthy full-term infants have been studied in their 2nd, 10th, 18th and 26th weeks of life in three standard situations: before feeding, in the course of milk drinking and after feeding. A polygraphic record of sucking, breathing, swallowing, the oculomotor activity, the EEG and vocalization has been taken simultaneously with a video-recording of the infant's behaviour. Physiological patterns and developmental changes of sucking, breathing and swallowing are described. These activities are considered as fine motor activity of the earliest age. The possibility of using polygraphic recordings of these variables for the diagnosis of the neurological syndrome called feeding problems is discussed. Further, behavioural activities in above mentioned three situations and their developmental changes, are described. None of the infants, not even the smallest ones, were asleep in the beginning of feeding. On the contrary, their eyes were open and there were more eye movements during feeding than in other situations. In the authors' opinions, the situation of feeding has, especially in the first days and weeks of life, a special significance for the development of social interactions between the infant and the person taking care of him. The behaviour of a regularly fed infant in the second quarter of his first year seems to be no longer influenced in the periods proceeding and following the feeding act by the prandial cycle but rather by cognitive needs. The influences involved in the regulation of the behaviour of the youngest infants are discussed.