The descriptive epidemiology of Hodgkin lymphoma (HL) has demonstrated marked variation by age, sex, social class, and time, strongly suggesting both a role of environmental factors and the existence of etiologically diverse HL subtypes. There is increasing evidence that Epstein Barr virus (EBV)–positive and EBV-negative classical HLs define two variants with separate etiologies. The risk for both increases with family history, whereas immune dysfunction and infectious mononucleosis have been implicated in EBV-positive HL risk only. Despite being the less common of the two, the natural history of EBV-positive HL is currently the best understood, both with respect to how EBV may contribute to malignant cell transformation and in relation to constitutional and environmental risk factors. Meanwhile, the understanding of the natural history of EBV-negative HL is meager. Future research for EBV-negative HL is expected to focus on its presumed infectious etiology, for which there are currently no strong candidates.