The γ–herpesviruses are a group of related agents which share the same broad strategy for infection of and persistence within the lymphoid tissues of their hosts. Yet in evolutionary terms these agents are sufficiently diverse to display multiple different molecular mechanisms whereby that strategy can be achieved. Attempts are made to relate the different in vitro growth transforming capacities of the γ1–herpesviruses, the T–lymphotropic γ2–herpesviruses and the B–lymphotropic γ2–herpesviruses to what is known about the biology of these virus infections in their natural or in experimental hosts. The review then summarizes the evidence linking γ–herpesviruses with oncogenesis and proposes that the diverse spectrum of Epstein–Barr virus and human herpesvirus 8–associated human tumours falls into three pathogenetically distinct categories. Many questions remain unanswered in the areas of γ–herpesvirus biology and disease pathogenesis: resolving these questions will require a broadening of our experimental approaches and a willingness to relinquish ‘single–model’ panaceas.