Following prolonged water logging due to heavy rainfall in Mumbai during July 2000, a total of 102 patients clinically suspected of leptospirosis were admitted in our hospital. Blood samples were examined for the presence of leptospires by dark ground microscopy (DGM) and IgM antibodies were detected by ELISA. Out of 102 blood samples, 37 were positive by ELISA giving a positivity rate of 36.27%. Of these, only 24 were positive by DGM. Out of the positive cases, 37.83% had respiratory symptoms, 32.43% each had jaundice and conjunctival suffusion and 16.21% had renal involvement. Mortality amongst the positive cases was 10.81%. Apart from hepatic and renal involvement, respiratory symptoms due to leptospirosis are on the rise.