A systematic investigation was undertaken to determine whether changes with age in infant attachment behaviors follow a developmental progression. Five groups of female infants, ages 8, 11, 14, 19, and 24 months were observed individually, within their respective homes, in a series of six 3-min episodes which involved varying types of separation. All attachment behaviors manifested at 10-sec intervals were recorded by the experimenter. Two classes of responses were monitored: (1) proximity behaviors – signalling, approach, and search, and (2) contact behaviors – sensorimotoric, perceptual (auditory, tactual, and visual), and conceptual symbolic behaviors. Data analyses yielded partial support for the hypothesis that the evolution of proximity behaviors follows an order of increasing complexity, beginning with signalling as the dominant means, followed by approach, and lastly, search. Some support was also obtained for the hypothesis that the evolution of contact behaviors follows the order of means whereby experience is constituted, beginning with sensorimotoric operations as the dominant means, followed by perceptual operations, and lastly, conceptual-symbolic operations. Findings were interpreted as indicating that changes with age in attachment behaviors follow a progression consistent with the orthogenetic principle of development.