Background: Leptospirosis is a public health problem, the severe form of which (Weil's disease) includes acute respiratory distress syndrome, typically accompanied by acute kidney injury (AKI), and is associated with high mortality rates. Recent evidence suggests that dialysis dosage affects outcomes in critically ill patients with sepsis-induced AKI. However, this population varies widely in terms of age, gender, and concomitant conditions, making it difficult to determine the appropriate timing (door-to-dialysis time) and dialysis dosage. Design, setting, participants, and measurements: It is logical to assume that increasing the dialysis dosage would minimize uremic complications and improve outcomes in such patients. Patients with Weil's disease constitute a homogeneous population and are typically free of comorbidities, therefore presenting an ideal model in which to test this assumption. Results: The effects of dialysis dosage were evaluated in this population, with the use of either classic or slow low-efficiency hemodialysis, and two periods/treatment plans were compared: 2002 to 2003/delayed, alternate-day dialysis (DAdD group; n = 15) and 2004 to 2005/prompt and daily dialysis (PaDD group; n = 18). Age, gender, AKI severity, APACHE score, serum urea, and time to recovery of renal function were assessed. All patients received vasoactive drugs (because of hemodynamic instability) and were on mechanical ventilation (because of acute respiratory distress syndrome). Mean serum urea during the dialysis period was significantly lower in the PaDD group than in the DAdD group. Of the PaDD group patients, three (16.7%) died, compared with 10 (66.7%) of the DAdD group patients. Conclusions: On the basis of this result, it is believed that alternate-day hemodialysis is no longer appropriate for critically ill patients with Weil's disease.