High titres of antibody to Epstein-Barr virus (EBV) late genes identify individuals at risk of developing endemic Burkitt's lymphoma (eBL). Viral lytic cycle early and intermediate-early gene expression in BL is associated with a favourable tumour response to chemotherapy. Our study investigated whether serological data identifying antibody expression to zta, a viral function that activates lytic-cycle gene expression, correlate with expression of its gene in tumours, and could have prognostic value. Studies on 10 Malawian patients, with presumed BL on clinical grounds, showed good correlations, suggesting that serum antibody responses might predict treatment responsiveness. The results with 1 patient were particularly striking. When admitted in January 1998, prognosis was poor as he was unable to walk, and had tumour cells, characteristic of stage IV disease, in his bone marrow. Laboratory investigations showed particularly high levels both of serum zta antibodies and of gene expression in his tumour. Follow-up confirmed him alive 6 months after hospital discharge. Among the EBV-positive cases, 2 were ultimately diagnosed as rhabdomyosarcoma, a tumour not previously associated with this virus. The findings from this small study, if confirmed, should have value for future BL management in resource-poor parts of the world.