This document discusses the importance of pre-operative liver function assessment prior to liver surgery. It outlines several methods of evaluating liver function, including clinical scoring systems like the Child-Turcotte-Pugh score, dynamic tests that measure hepatic uptake and excretion such as indocyanine green retention and nuclear scintigraphy, and volumetric measurements using CT scans. No single test can fully assess liver function, so a combination is recommended, along with surgical judgment, to determine the severity of any underlying liver disease, tumor extent, predicted post-operative liver remnant, and risk of hepatic failure. This helps select appropriate patients and procedures to optimize surgical outcomes.