The methods for causality assessment of adverse drug reactions were developed in the 1970s and 1980s, alongside the development of pharmacovigilance. The French method is one of the earlier of these, following on from the pioneering works by Irey and Karch and Lasagna. Initially published in 1978, it was updated in 1985, and again in 2011. The main alterations to the original method are presented in tables annexed to this paper. The successive versions improved the presentation, provided more formalised definitions of the criteria for assessing causality, while at the same time ensuring the method remained easy to use. Causality assessment enables the causal link between a drug and the occurrence of an adverse reaction to be formalised and explained. It contributes to diagnosis, and to determining the action to be taken in case of an adverse drug reaction. It can contribute to the quality and the relevance of the data stored in pharmacovigilance databases.