Seventy-two deaf Ss (10- to 19-years-old) were tested, employing the Test of Syntactic Ability (TSA), the language sub-tests of the Stanford Achievement Test (SAT), and analyses of written language samples, in a study of the influence of early language and communication environment on their later syntactic language ability. Ss were divided into four groups: the Manual English (ME) Group whose parents were deaf, had a good command of English, and used manual communication in the form of Manual English; the Average Manual (AM) Group whose parents were deaf, had language showing gross deviations from Standard English, and used manual communication with the Ss from infancy; the Intensive Oral (IO) Group who had been enrolled in a formal Oral educational program and whose parents had received formal training in using oral methods exclusively and intensively with their children; and the Average Oral (AO) Group who had been enrolled in a formal Oral educational program and whose parents had received no formal training in oral methodology. Results showed significant superiority of the ME group over the two Oral groups on five of the six test structures of the TSA; and significant superiority of the ME group over the other three groups on all four sub-tests of the SAT. (Author/LS)