During the last decade, knowledge about cholestatic liver disease and concomitant diseases, such as ulcerative colitis, cholangio- and hepatocellular carcinoma, pancreas and colon cancer, has increased considerably. Studies on ursodeoxycholic acid treatment alone or in combination with immunosuppressive compounds and their positive effects on biliary liver disease as well as on so-called overlap syndromes or intestinal tumors are published in increasing numbers, and stimulate discussion on whether or not ursodeoxycholic acid is able to improve the general condition and/or life expectancy of patients. On the other hand, genetics, aetiological and pathogenetic aspects are still difficult to comprehend, but are the absolute prerequisite for the development of better treatment options. This book is the proceedings of Falk Symposium No. 136 (Part I of the XII Falk Liver Week, held in Freiburg, Germany, on October 15-16, 2003), and contains stimulating, exciting and controversial papers on clinical and also basic research at the highest scientific level.