A 47-year-old patient with severe decompensated alcoholic liver disease developed a progressive deterioration of her renal function (serum creatinine 4.0 mg/dL) with a renal failure index (RFI: UNa/U/PCr) consistently less than 1.0. In the absence of other causes of renal failure, these values supported the diagnosis of hepatorenal syndrome (HRS). A five-hour head-out water immersion (HWI) in a sitting position was carried out to increase the patient's "effective" blood volume (EBV) in an attempt to reverse the HRS. Hemodynamic monitoring (Swan-Ganz) was performed during the entire HWI procedure. Cardiac index increased by 64% during HWI (2.57 to 4.22 L/min/m2). Stroke volume index doubled (32.9 to 65.0 mL/m2) and systemic vascular resistance decreased by 48% (1426 to 754 dyne sec/cm). Increases in right atrium (RA) pressure (7.5 to 17.5 mm Hg) and pulmonary wedge (PW) capillary pressure (7.5 to 16.3 mm Hg) also occurred. Hemoglobin, hematocrit, and plasma protein concentrations decreased by 18% during HWI. Only a modest improvement in creatinine, urea, inulin, and para-aminohippurate (PAH) clearances was observed during HWI, and the RFI remained below 1.0. Plasma levels of antidiuretic hormone (ADH), aldosterone, and renin activity decreased during HWI. The patient's renal function progressively deteriorated over the next 15 days, but tubular function, as assessed by an RFI less than 1.0, was still intact seven days after our study. Our results indicate that a considerable increase in effective blood volume does not restore renal function in HRS.