Abstract: In basic studies, infrared ray television pictures of rats' livers were made with the aim of: (1) assessing, continuously and correctly, changes over time in liver surface coloration following an intravenous injection of Indocyanine green (ICG) and (2) quantifying the degree of ICG coloration of areas of the liver surface of interest by changing the image obtained into electrical signals and thereby obtaining an objective measure of coloration status. An Olympus CLE‐F10 (Olympus, Tokyo) was used as a light source for infrared ray TV imaging, while a monochromic CCD camera (Toshiba, Tokyo) was used as a television camera, with a visible light cut filter attached to the eyepiece of the scope. By means of a video mean densitometric apparatus (Hoei, Tokyo) the degree of ICG coloration was determined as a luminosity, which was recorded after being changed into electrical signals. Infrared ray television imaging made it possible to distinguish areas of shades of coloration even after an intravenous injection of ICG in as small dose as 0.5 mg/kg. It made a continuous clear record of changes over time in the coloration of ICG‐stained liver surface areas. The changes in the degree of coloration of the liver surface recorded as luminosity consisted of an early, steep component (vascular phase) and a subsequent slow component (parenchymal phase).The vascular component was influenced by the dosage of ICG while the parenchymal phase was influenced by the severity of hepatic injury.