The article deals with the problem of the transition from the Latin sentence structure, whose basic word order was SVO to the sentence structure of the old Romance languages interested by a V2 type system. After a short description of the V2 system of the old Romance languages (section 1) the main phenomena characterizing the Latin word order are considered and a hypothesis on the Latin word structure accounting for the basic word order and the main marked orders is advanced (sec. 2). Starting from the idea that the new Romance order has developped from a word order possible in Latin, two hypotheses - already put forward in the discussion of the problem in the Romance domain and for parallel phenomena of the Germanic languages - are considered. That the V2 system had developped 1) starting from the Latin sentences with verb initial, or 2) starting from the sentences where the weak/clitic forms of the verb SUM were in the Wackernagel position (i.e. after the first constituent of the sentence). On the basis of speculative arguments (sec. 3) and evidence given by the late and vulgar Latin texts (sec. 4) preference to the first hypothesis is given and the details of the mechanism responsible for the linguistic change are elaborated (sections 3-5).