Levels of plasma tumour necrosis factor-alpha (TNF-alpha) were determined consecutively in 42 patients with burns > 20 per cent of the total body surface area using an enzyme-linked immunosorbent assay. In the early period after injury (including the period of burn shock), 24 patients had detectable TNF-alpha levels in their plasma. However, the plasma TNF-alpha levels at the time of admission were very low and did not correlate with the extent of the burn or the prognosis. In contrast, the maximum plasma TNF-alpha level over the whole clinical course was significantly correlated with the area of the burn and the prognosis. No correlation was found between the plasma TNF-alpha and plasma endotoxin levels. TNF-alpha may be produced locally in infected burns and monitoring of plasma TNF-alpha levels may be a useful prognostic indicator for burns patients.