Leptospirosis is a widespread spirochetal zoonosis caused by the members of the genus Leptospira. The natural history of human leptospiral infection varies widely. The infection can cause a subclinical illness, or may be mistaken for influenza. In individuals who become ill, leptospirosis typically presents as one of two clinically recognizable syndromes. The first syndrome is the mild anicteric form, which rarely results in death, while the second syndrome fulminant icteric form, known as Weil's syndrome, has an associated 10% mortality. The anicteric form comprises two disease stages, namely the septicemic phase and the immune phase. In fever work up, leptospirosis is usually not the first considered pathogen of sepsis, unless jaundice and ARF are present. This study investigated two patients with leptospirosis presenting with conscious disturbance and oligoric acute renal failure individually. In the second patient, persistent hypokalemia and metabolic alkalosis developed during recovery from acute renal failure. Several tubular function tests were performed to define the renal tubular lesion in this patient, revealing a defect on the thick ascending limb. This study also reviews previous studies on leptospirosis including its epidemiology, pathogenesis, clinical presentation, diagnosis, treatment, and prognosis.