In order to specify the factor structure and stability of infant and maternal behavior, mother/infant interaction was observed when infants were 12 and 24 months of age. Mothers and infants observed in dyadic interaction in a playroom during a 15-minute free play period represented a heterogeneous sample across gender, socioeconomic status, and birth order. Interactions were recorded on checklists which contained 18 infant and 18 maternal behaviors. The observed behaviors are listed in the text. Two factor analyses were performed at each age level: one for the infants' behavior and one for the mothers' behavior. Subsequently, an oblique factor rotation with a delta value of zero was employed to determine unique dimensions of social behaviors while allowing for the identification of overlap between dimensions. Rotated factor solutions were examined and factors were identified using criterion levels of eigenvalues, loadings, and communality. After a specified number of factors had been determined to be most psychometrically and theoretically useful, the factor analyses were conducted a second time. Results are discussed. (Author/RH)