BACKGROUND: The pattern of liver function tests (LFTs) in community-acquired pneumonia has not been investigated in detail. Although abnormal tests are thought to be more frequent in patients with atypical pneumonia, the prognostic value of LFTs have not been clearly established. METHODS: We assessed 96 consecutive patients admitted to one hospital with a chest infection over a period of 6 weeks. The infection was classified as bronchitis or lobar pneumonia on clinical and radiological criteria. The site and severity of the infection were assessed and correlated with LFTs and standard British Thoracic Society prognostic criteria. Mortality and length of stay in survivors were used as major outcome measures. RESULTS: There were 17 deaths (18%) overall and patients with abnormal LFTs were significantly more likely to die than those with normal tests (25% vs. 5%; p=0.026). Length of stay was significantly longer in survivors with abnormal liver function than in those with normal tests (9.7 vs. 5.8 days; p=0.006). A low albumin was the most useful predictor of poor outcome and carried a relative risk of dying of 1.8, comparable to the predictive value of tachypnoea. ALT was increased threefold in those succumbing to their disease, but alkaline phosphatase levels were not predictive of outcome and an increase in gamma GT appeared to be protective. CONCLUSIONS: Abnormal LFTs are common in community-acquired pneumonia and are of prognostic value. Patients with a low albumin or raised ALT are significantly more likely to die from their disease or to stay in hospital for a prolonged period. However, other LFTs are of less value in predicting prognosis.