The types of syntactic errors made by children learning a second language provide insight into the way in which children acquire the second language. The contrastive analysis hypothesis states that while the child is learning a second language, he will tend to use his native language structures in his second language speech; where there are differences between the two languages, he will make mistakes. The L2=L1 acquisition hypothesis holds that children actively organize the L2 speech they hear and make generalizations about its structure as children learning their first language do. The mistakes expected in such a situation would be similar to those made by children learning that same language as their first language. Error analysis in terms of the two theories is discussed, and the authors present their own hypothesis for error explanation and language development. (VM)