In order to assess the safety of 1-h infusions of amphotericin B (AMB), we prospectively monitored 213 1-h infusions of AMB (dose range, 0.27 to 0.89 mg/kg of body weight) in 27 patients with creatinine clearances of > 25 ml/min. Holter monitor tracings during 1-h infusions were compared with those during a 4-h baseline period of monitoring. There were no ventricular dysrhythmias during 1-h infusions of AMB that were not present during baseline monitoring. Nausea and/or rigors were noted for 32 (15%) infusions in six (22%) patients. No patient exhibited a temperature rise of > 1 degree C. We conclude that, in doses of up to 0.9 mg/kg, AMB does not appear to induce asymptomatic ventricular dysrhythmias when administered over 1 h to patients with creatinine clearances of > 25 ml/min.