5 patients with primary biliary cirrhosis (PBC), 9 patients with compensated hepatic cirrhosis of different etiology and 12 control persons were tested for renal acidification after peroral CaCl2 administration and urine Na2SO4 and pCO2 infusion as well as the gradient between partial urine pressure and blood pressure after NaHCO3 application. Distal renal tubular acidosis (DRTA) was diagnosed in one patient with PBC, latent DRTA in other 2 patients with PBC. Not even one patient's acidification disorder was eliminated through an increased sodium application to the acidification site after Na2SO4 application. After NaHCO3 application, the gradient between the CO2 partial pressure in the urine and blood in both patients with PBC was, however, latent, DRTA normal. After pH gradient elimination in patients with PBC and DRTA, the hydrogen iont secretion is thus comparable with the control persons. Based on this study, the authors believe that the gradient type of DRTA is characteristic of primary biliary cirrhosis.