To investigate the safety, pharmacokinetics, pharmacodynamics, and efficacy of OPC-41061 in patients with chronic renal failure undergoing hemodialysis or hemodiafiltration using variables, such as daily urine volume and increase in interval body weights between hemodialysis or hemodiafiltration, in 4-day intermittant administration (excluding the days of hemodialysis or hemodiafiltration) at the dose fixed during the dose-escalation period