The Liver Cancer Study Group of Japan established a classification of macroscopic type and the TNM staging of intrahepatic cholangiocarcinoma (ICC). With the observation of more than 240 resected cases of ICC, three fundamental types were established. They were: (1) mass-forming (MF) type, (2) periductal-infiltrating (PI) type, and (3) intraductal growth (IG) type. The MF type forms a definite mass, located in the liver parenchyma. The PI type is defined as ICC which extends mainly longitudinally along the bile duct, often resulting in dilatation of the peripheral bile duct. The IG type proliferates toward the lumen of the bile duct papillarily or like a tumor thrombus. The TNM classification of ICC was then designed, using 136 cases of the MF type resected curatively between 1990 and 1996 at member institutes. Univariate and multivariate analyses showed: (1) tumor 2 cm or less, (2) single nodule, and (3) no vascular and serous membrane invasion as prognostic factors. T factors were defined as follows: T1 is an ICC that meets all requirements of factors (1), (2), and (3); T2 meets two of the three requirements, T3 meets one of the three requirements and T4 meets none of the three requirements. Our data did not support the idea that the hepatoduodenal lymph node is regional. The N factors were defined as N0 no lymph node metastasis; and N1, positive at any nodes. Thus, the stages of ICC were defined as stage I, T1N0M0; stage II, T2N0M0; stage III, T3N0M0; stage IVA, T4N0M0 or any TN1M0; and stage IVB, any T any NM1.