In this paper we describe an approach to acquire synonyms for French automatically that is easy to port across domains and across languages. The approach relies on automatic word alignments in parallel texts and uses distributional methods to compute the semantic similarity of words based on these word alignments. As a result the system outputs ranked lists of candidate synonyms for a given word. We compare the performance of the system with a system that uses syntactic contexts to acquire synonyms automatically. Evaluations are done on a large-scale French synonym dictionary. We show that the alignment-based method outperforms the syntactic method by a large margin. In addition we show that the method can easily be ported to a different language and to a different domain.