Recent advances in technology have greatly impacted upon the practice of nuclear medicine in general, and the approach to hepatobiliary diseases in particular. Empha sis is now placed more on non-invasive functional imaging with quantification, a feature unique to nuclear medicine and not available from any other competing diag nostic imaging modality. By providing a measure of severity of disease, quantification aids not only in timing of therapy but also for testing whether or not the chosen therapy has achieved the intended goals and objectives. This is the first textbook of its kind in the new millennium on nuclear hepatology to fully integrate quantitative physiology with morphology in the diagnosis of hepatobiliary diseases. The conception of nuclear hepatology occurred in the late 1940s with the introduc tion of radiocolloids, whose rate of clearance from blood was used as a measure of hepatic blood flow. Radiocolloid imaging of the liver, introduced first in the mid 1950s, was the most popular nuclear medicine imaging procedure in the 1970s and early 1980s, accounting for nearly 50% of the total workload in many nuclear medicine departments.