Through the figure of the god Lug, this article tackles the issue of how to conduct research in Irish mythology. As regards the choice of sources, the answer of the debate between an approach based on Irish medieval literature and an approach that integrates other cultural and geogra- phical areas lies in the ability to find consis- tency between all the information used for the study. As regards interpretation of Irish medieval literary contents, our more and more precise knowledge of this material brings to light the difficulty in identifying with certainty elements which exclusively come from oral tradition or/and pre-Chris- tian time. The example of the links of the god called Lug with horses and assemblies tends to show that Irish literature is not to be considered as a monolithic corpus, but rather a corpus shaped by different in- fluences and having various origins.