Using the freshwater stingrays Potamotrygon spp. and the balloonfish Diodon holacanthus, an investigation was carried out on the liver size and the amount of fat droplets in hepatocytes and the following results were obtained. The liver of the stingrays was relatively small in size among Chondrichthyes and the value of hepatosomatic index (HSI) on six specimens was 3.17±0.27% (mean±S.E.). On the other hand, the liver of the balloonfish was relatively large in size among Osterichthyes and the value of HSI on three specimens was 5.74±0.38%. As for the fat droplets in hepatocytes, their accumulation was conspicuous in both species of fishes. Thus, the livers in the freshwater stingrays and the balloonfish were confirmed as the so-called “physiologi-cally fatty liver.”