Aim: Presentation of leptospirosis as a cause of acute renal failure. Leptospirosis is an infectious zoonosis caused by the pathogenic spirochetes of the genus Leptospira, typically Leptospira interrogans. The main reservoirs of Leptospira are rodents, wild animals, dogs, cats, pigs, domestic cattle and horses. The primary source of infection is exposure to water, soil or plants contaminated by the urine of infected animals. The clinical picture of leptospirosis ranges from a mild disease with non-specific (flu-like) symptoms to a severe form with liver and kidney failure, impaired consciousness and meningitis. The case report presents leptospirosis with acute renal failure in a 17-year-old boy. Due to the fact that prior to the development of the disease the boy stayed in a country where leptospirosis is endemic (Thailand), a suspicion of the disease was raised, and subsequently confirmed serologically by an immunoenzymatic test. Conclusions: The diagnosis of an imported disease, including leptospirosis, should be taken into consideration in patients with flu-like symptoms accompanied by acute renal or hepatic failure who have a history of recent travel to tropical areas.