The present study makes an inventory of the ways in which “pro”, one of the new prepositions in the Romanian language, functions. This preposition is of Latin origin, but it has been reactivated in the contemporary language with the following meanings: “for”, “in favour of”, “in support of”. We are going to analyse: the functions which are fulfilled in a statement by the term dominated by the preposition, the meanings of the preposition and the restrictions imposed by it on the dominated term. We are also going to examine the structures in which the preposition “pro” is associated with the preposition “against”, in order to reveal the morphological status of the two elements.