Leptospirosis is a re-emerging infectious disease affecting both animals and humans worldwide. This infection is associated with occupational contact with animals, recreational exposure and contact with leptospires as a consequence of flooding. Multiple organ involvement may be encountered in acute severe leptospirosis and early renal involvement is commonly characterized by tubulo-interstitial nephritis and tubular dysfunction. Leptospirosis has been increasingly recognized as an important infectious disease in Taiwan since 1997 and Leptospira santarosai serovar Shermani is the main serovar encountered. The most common presentations are fever, jaundice and acute renal failure. This triad presentation in patients with acute multiple organ dysfunction should alert physicians to the possibility of leptospirosis. Penicillin treatment is effec- Dr. Chih-Wei Yang tive and may dramatically save patients from multiple organ failure provided it is given early. The rapid IgM assay may aid screening of Leptospirosis, thus allowing effective treatment to be initiated early. Leptospirosis appears to be underestimated in Taiwan and affects at least 10% of patients with multiple organ dysfunction. Therefore, a high level of clinical suspicion may help in identifying underestimated leptospirosis in Taiwan.