Leptospirosis is a zoonosis with protean clinical manifestation. Diagnosis requires a high index of suspicion and is confirmed by isolation of the organism or, more commonly, by serologic studies. In the fall of 1987, after severe flooding, we saw 93 patients with leptospirosis, confirmed by a microagglutination test. Thirteen percent of the patients had no clinical or laboratory findings except fever and headache, but the rest had mild to severe manifestations. Jaundice, renal failure, and aseptic meningitis were not common, but pulmonary symptoms, when present, were striking. The mortality rate was 5%. The main cause of death was asphyxiation due to massive hemoptysis from pulmonary hemorrhage and acute respiratory failure.