The present invention relates to an automatic translation method.When a sentence in a source language is translated into a sentence in a target language, the method comprises: a step (1) of extracting the set of sentence portions of the target language from a textual database that correspond to a total or partial translation of the source sentence to be translated; a step (2) of determining all the assemblies of these target sentence portions that overlap the source sentence; a step (3) of choosing the best assemblies according to a criterion of maximum overlap between the target sentence portions assembled in the preceding step and according to a criterion of minimizing the number of assembled elements; a step (4) of determining the target sentence by choosing the best assembly according to coherence criteria. The invention is notably applicable to the translation of texts in a rare language.More generally, it applies to translation with no previously established bilingual texts.