This observational study examined the development and use of communication in a pair of deaf and hearing monozygotic twins from 13 months of age until 36 months of age. One twin contracted meningitis at 7 months, leaving her profoundly deaf but without other measurable sequelae. The other twin is normal in all respects. The prelingual twins were enrolled in a total communication preschool program where, with their parents, they participated in activities designed to enhance the language skills of deaf children. The twins were videotaped monthly, first at their preschool program and later at home. All forms of communication were recorded, including signs, vocalizations, and hand and body gestures. Additionally, eye gaze direction and body positions during communication were noted. Comparisons between the deaf and hearing twins showed that although both children were able to learn language and communicate successfully, the hearing twin preferred a vocal form of language, whereas the deaf twin used mostly sign language. Moreover, the hearing twin's communication was usually responsive, while the deaf twin's communication was comprised mostly of imitative signs and gestures. Methods of teaching a profoundly deaf child to communicate are discussed.