Four cases revealed high retention of ICG test and normal retention of BSP test were reported. The results of liver function test of these cases showed within normal limit except ICG retention. ICG disappearance rate ranged from 0.017 to 0.025, whereas BSP disappearance rate ranged from 0.069 to 0.126. The transfer rate of ICG from plasma to liver markedly decreased by two compartmental analysis of the decay curve and slightly reduced transfer rate of BSP from plasma to liver was also observed. The step on both ICG and BSP disappearance curve was observed during 20 to 25 minutes after the injection in all cases and in repeated observations. The step formation is one of the characteristic changes in these cases. The ICG binding capacity of serum protein decreased in the first peak and increased in the third peak eluted by gel filtration of Sephadex G-200. Light microscopic findings of the liver showed normal histology. The electronmicroscopic findings showed the increase of lipofuscin-like lysosome, modification and paracrystalline like array of mitochondria and increase of reticulum fiber in Disse's space. Father of a case showed ICG retention without BSP retention. From these results it is suggested that these cases are a new type of dye excretory disorder of liver with heredity or constitution.