One of the important causes of acute febrile illness in a country where malaria, typhoid and dengue are also not uncommon, leptospirosis, a zoonotic disease spread by rodents, is endemic in Tamil Nadu, Kerala and Andamans; and is now being increasingly reported from other parts of India, perhaps with better facility to diagnose the disease. Disease of profound importance in view of its grave outcome, in its icteric form (Weil's disease), may have a mortality of as high as 40%. Worst prognosticator is the presence of multi-organ failure (MOF), as in any other septicemia. Andaman hemorrhagic fever (AHF), a type peculiar to Andamans, is now being described elsewhere in the country also. IgM ELISA, Dot-ELISA, dip-stick method and slide agglutination test (SAT) are newer screening methods for diagnosis of leptospirosis, but are only genus-specific. Identifying specific serovar is possible by Micro-agglutination test (MAT) and culture method only. Anicteric type of disease, however, is easily treatable with penicillin and has a good prognosis. Oral doxycycline can be used for prophylaxis during the risk of exposure.