Studies on peer interaction in infancy seem to imply that social group structure emerges from infants' and toddlers' dyadic interactions. In contrast to this position, the present study hypothesizes that attention structure may be a major precursor for social group structure. To investigate that possibility, an attempt was made to develop a reliable and valid research instrument suitable for assessing the group structures of very young children. Four groups of infants 6 to 11 months of age were observed in groups of four or five at weekly intervals over a period of 3 months. Videotapes of the second, eighth, and fourteenth session were used for observational analysis. Over a continuous period of time totalling 15 minutes, the duration and orientation patterns of the subjects' behavior were coded. Additionally coded were quality of attention, social approach, and social interaction. Thus the coding scheme allowed for quantitative and qualitative analysis of the data for each individual child over time as well as for the group situation at each point in time. Results indicated the existence of group structures beyond dyads. Infants' social positions within group structures were cross-validated with qualitative indices of social competence. Applications for developmental research focusing on infants' social development are discussed. (Author/RH)