Leptospirosis is a zoonosis caused by a gram negative aerobic spirochete of the genus Leptospira. It is acquired by contact with urine or reproductive fluids from infected animals, or by inoculation from contaminated water or soil. The disease has a global distribution, mainly in tropical and subtropical regions that have a humid, rainy climate and is also common in travelers returning from these regions. Clinical suspicion is critical for the diagnosis and it should be included in the differential diagnosis of any patient with a febrile hepatorenal syndrome in, or returning from endemic regions. The leptospiremic phase occurs early and thereafter there is an immunologic phase in which the most severe form, Weil's disease, occurs. In the latter, multiple organ dysfunction predominates. The appropriate diagnostic test depends on the stage of the disease and consists of direct and indirect detection methods and cultures. Severely ill patients need to be monitored in an ICU with appropriate anti-bacterial agents and early, aggressive and effective organ support. Antibiotic therapy consists of penicillins, macrolides or third generation cephalosporins.