The responses of serum IRI, serum IRG, and blood sugar levels to 75 g oral glucose and serum IRI to glucagon injection were investigated in 26 chronic hepatitis, 20 liver cirrhosis, 5 primary sclerosing cholangitis (PSC) and 8 healthy volunteers served as controls. The results obtained herein were as follow: 1) The frequency of the glucose intolerance in PSC was higher than the other liver diseases. The mean values of the insulinogenic index (delta IRI/delta BS 30 min) in PSC was lower than control subjects. No suppression of IRG by glucose was observed in PSC. 2) The maximum IRI value (max delta IRI) in PSC during glucagon test was lower than that in control subjects. 3) In one case of 5 PSC ICSA was founded to be positive. These data suggest that we should pay much attention to suffering from diabetes mellitus in natural history of PSC.