Legionella pneumophila is the second most common cause of severe community-acquired pneumonia requiring treatment with intermittent positive pressure ventilation. The prognosis of this condition and its complications have not been well documented. Erythromycin is the first-line antibiotic of choice based on clinical experience. Rifampicin has been recommended as an additional agent, though clinical experience has not been reported. We have retrospectively examined 30 cases of severe community-acquired legionella pneumonia. The mean age of the patients was 53 years, 24 were male and eight died (27%, mean age 57 years). During admission 26 patients received erythromycin (eight died) and 15 received rifampicin in addition (five died); four received neither drug and survived. Mean duration of intermittent positive pressure ventilation was 15.9 days for survivors and 14.1 days for fatal cases. Acute renal failure requiring dialysis developed in 13 (43%), of whom five died (38%). Positive inotropic drugs were used in 10 patients and of these six died. Jaundice occurred in 11 patients and was significantly more common (p = 0.028) in patients who received rifampicin (60%) than in those who did not (17%). Excess bilirubin was largely conjugated when measured and there was no consistent hepatitic or obstructive change in the liver enzymes. Severe community-acquired legionella pneumonia has a relatively good outcome with a mortality of 27%, though prolonged intermittent positive pressure ventilation may be required. Acute renal failure is common but reversible in survivors, and jaundice is more common in those who receive rifampicin.