OBJECTIVE Acute cholecystitis in critically ill patients has a high morbidity and mortality. We observed a number of patients presenting with Legionella pneumonia and acute renal failure who subsequently developed acute cholecystitis. There has previously been no reported association between Legionella pneumonia, renal failure and cholecystitis, prompting this examination of the cases and review of the available literature. METHODS The Western Hospital patient record discharge codes (DRG) from 1993 to 2001 were searched retrospectively for all cases of Legionella pneumonia or acute renal failure requiring dialysis (ARF) at presentation or during their period of hospitalization. Acute cholecystitis was then included as a cross-search and results analysed. RESULTS Twenty-six cases of isolated Legionella pneumonia and 112 of ARF were identified with a further 10 having both conditions simultaneously. Of these 10 cases, three were identified as also having acute cholecystitis. The combination of Legionella pneumonia and ARF was associated with an increased risk of acute cholecystitis (P = 0.002) whereas neither condition in isolation demonstrated this association. CONCLUSIONS Patients with Legionella pneumonia can become critically ill with multiple complications including acute renal failure requiring dialysis. In this setting, they may have an increased risk of developing acute cholecystitis, which clinically can be difficult to ascertain. Diagnosis requires a high index of suspicion and vigilance.