Events surrounding infection and disease in infectious mononucleosis are a model for epidemiological factors that may affect the phase of initiation, the phase of promotion and the phase of tumour development in African Burkitt's lymphoma (BL). Consideration of the circumstances of early Epstein-Barr virus (EBV) infection as the initiator, and of malaria as the promoter, of African BL reveal some shortcomings in the evidence incriminating malaria. Possible factors leading to the emergence of the clinical tumour suggest that other factors may be involved. The absence of EBV and malarial infection in some cases of American BL indicate that they are neither necessary nor sufficient causes of the tumour in all settings.