This chapter discusses some of the parallels between the processes of first and second language acquisition and pidginization and creolization. It looks at the field of second language acquisition, where there has been a debate between the role of universals vs. transfer in the development of learner varieties. The chapter provides a more detailed comparison of the similarities and differences between first and second language acquisition and pidgins and Creoles in one area of grammar, namely, relativization. It also discusses the foreigner talk theory of pidgin origin. The chapter also provides some of the basic concepts which have emerged in the context of the study of transfer and interlanguage. It argues that it is the exploitation of this route of grammaticalization which the child's acquisition of relative clauses has in common with the development of relative clauses in pidgins and Creoles. The chapter also looks at the process of children's acquisition of relatives.