Studies on the acquisition of relative clauses are reviewed. Two polarities among a variety of possible approaches are: Slobin's (1971) study that emphasizes acquisition process and learning strategies, and studies like Sheldon's (1974) that emphasize the linguistic structures involved. Early proposals that children experience more difficulty in processing discontinuous, as distinct from contiguous elements, have been contradicted by the parallel function hypothesis. More recent studies tend to emphasize an examination of the processing heuristics used by children, and they show that at times children have no adequate processing strategies. Most studies of relative clause acquisition report on experiments in which children were instructed to act out the content of sentences containing relative clauses by manipulating toy animals. By observing children's responses over the course of many experiments, investigators have been able to systematize children's responses into a number code of response types, which can be classified into a particular sentence type. All of the reviewed studies have in common that they suggest new avenues of approach to an understanding of children's acquisition of relative clauses. (SW)