Nowadays, non-hodgkin lymphoma (NHL) presents the fifth highest cancer incidence rate. It is one of the few cancers in which incidence has been increasing over the last decades in the world. Even though therapeutic progress allow a favourable evolution in one case out of two, NHL remains preoccupying, especially because of the lack of knowledge regarding its aetiology. Indeed, several factors have been studied and may play a concomitant role: factors linked to genetics, immunodepression, viruses, professional or non-professional toxics. We will review results from different studies evaluating the role of those factors after having reported current knowledge on NHL.