The development of vocalization during the first 3 months of life was investigated in 2 groups of subjects: infants born to congenitaUy deaf parents; infants born to normally hearing and speaking parents. One of the infants born to the deaf was himself born deaf. Twenty-four hour tape recordings were made every other week and the data were analyzed qualitatively, quantitatively, and longitudinally. Despite the dramatic differences of environment and parental ability to respond to the infants'' sounds that distinguished the 2 groups of subjects, no essential differences could be detected in the vocalization of babies in the 2 types of homes. Evidence seemed to indicate that crying and the emergence of cooing are dependent upon maturational readiness. They are responses to internal states, elicited at first by rather non-specific environmental events. Subsequently crying and cooing go through separate and very different developmental histories.