The purposes of this study were to investigate the language use and language development of blind and sighted preschool children who were in the same daily environment by means of naturalistic, observational research and to field test the methodology for the investigation. The sample consisted of 12 children who were attending the Infant Care Center at the University of North Carolina at Greensboro. During each year of the study, 1980 and 1981, the vocalizations of two blind children were compared to those of the sighted boy and girl closest to them in age. The data were collected by observing each of the six (per year) subjects for 15 randomly selected minutes on 15 days. All vocalizations spoken by the subjects were recorded on observation sheets and classified by function. The percentage of each child's vocalizations in each category— spontaneous, response, imitated, and initiated—was computed and compared within each age group