1) Fluid retention and ascites are rarely seen in patients with primary biliary cirrhosis (PBC). In an attempt to clarify this clinical observation, renal handling of sodium, water and divalent ions was studied during extracellular volume expansion (ECVE) and maximal suppression of antidiuretic hormone (ADH) secretion in 5 patients with PBC and 9 normal subjects. 2) Mean fractional excretion of sodium, water, phosphate and calculated fractional distal delivery of sodium were significantly greater in patients with PBC as compared with normal controls. Fractional CH20 for given fractional urine flow was similar in patients with PBC and normals. 3) The data suggest that patients with PBC have a greater diminution of proximal tubular reabsorption of sodium in response to ECVE than controls. This augmented elimination of salt during ECVE in patients with PBC may explain the rarity of ascites and edema in this type of cirrhosis.