This paper presents the results of a longitudinal examination of syntactic skills, starting at the age of emergence of simple sentences and continuing through the emergence of complex sentences. We ask whether there is systematic variability among children from different socioeconomic backgrounds in the early stages of sentence production. The results suggest a different answer for simple versus complex sentences. We found a striking similarity across SES groups on the measures tapping early mastery of basic syntactic rules of simple sentences. At the same time, there was a significant difference between SES groups in the mastery of complex sentence structures. This difference emerged at the earliest stages of production of multi-clause sentences and persisted throughout the period of observation. The implications of these findings for the understanding of mechanisms of syntactic development are discussed.