This study of language acquisition in children between the ages of six and ten investigates their linguistic competence with respect to complex aspects of English syntax. Thirty-six children were tested for knowledge of nine complex syntactic structures. Five of the structures proved to be acquired in sequence, revealing five developmental stages in acquisition of syntax. The nature of specific disparities between adult grammar and child grammar are discussed, and the gradual reduction of these disparities as the children's knowledge of their native language increases is traced. Of particular interest is the regular order of acquisition of structures, accompanied by wide variation in rate of acquisition in different children.