Leptospirosis is a zoonosis caused by pathogenic Leptospira species. Leptospira infection can range from subclinical to life-threatening disease. Renal failure and severe respiratory symptoms may occur and are associated with a high mortality rate. It is important to realise that renal failure and other symptoms can occur in the absence of icterus. Leptospiraemia occurs mostly during the first week of acute illness, so blood cultures should be taken as soon as possible. Most cases of leptospirosis are diagnosed by serology. Antibodies are detectable in the blood approximately 5 to 7 days after onset of symptoms. Early recognition and treatment with either cephalosporins or penicillin may shorten the duration and severity of multi-organ failure and is therefore mandatory.