Lymphomas constitute a heterogeneous group of malignant disorders with different clinical behaviours, pathological features and epidemiological characteristics. For some lymphoma subtypes, epidemiological evidence has long pointed to infectious aetiologies. A subset of Hodgkin lymphoma is strongly linked to Epstein-Barr virus (EBV) infection. In addition, infectious agents can directly infect and transform lymphocytes (e.g. EBV, human herpesvirus 8), induce immunosuppression (human immunodeficiency virus), or cause chronic immune stimulation (hepatitis C virus, Helicobacter pylori), all of which may play a role in the development of various non-Hodgkin lymphoma subtypes. Here, we review the epidemiological evidence linking infections with malignant lymphoma.