A group of studies on child language development between ages 2 and 3 is presented. The studies, originally published between 1970 and 1989, are the result of a longitudinal research program. An introductory section describes the contents, offers background information on several different perspectives (developmental, learnability, cross-cultural) in language acquisition research, and outlines some conceptual themes (meaning in child language, context and child language, cognition and child language, individual differences, centrality of verbs) appearing in the studies. The first group of papers consists of studies of simple sentences and includes the acquisition of constituent structure and meaning relations and three kinds of complexity in simple sentences: negation, verb inflection, and wh- questions. The second section consists of the studies of complex sentences, including acquisition of syntactic connectives and clausal meaning relations, complementation, and complex sentences that express causality. The two papers in the third section pertain to process and interaction in language development. One is a study of role imitation in learning words and constituent structure; the other is a study of contingency in discourse. Four of the children studied appear in all the studies, and six others appear in one or two studies. (MSE)