Severe leptospirosis is frequent in Réunion Island during the summer, causing life-threatening multivisceral failure including meningitis and meningoencephalitis. Two cases of pure encephalopathic manifestations occuring in the course of leptospirosis have prompted us to report and discuss the features, outcome, and physiopathology of this rare syndrome. Hallucinations occurred after a few hours of hospitalisation, and disappeared after 24 hours of symptomatic treatment, patients nevertheless remembering the episode. Alcoholism definitely not the cause of this delirium tremens-like syndrome, a direct inflammatory, metabolic, or infectious process may be involved, as well as a potentially lethal penicillin-induced Jarisch-Herxheimer reaction.