In order to investigate the morphologic changes of hepatocyte by vitamin A deficiency, the author fed vitamin A deficient diet by Lamb's formula to male weanling Sprague-Dawley rats. Twenty rats were divided into two groups(14 as experimental group and the rest 6 as control). Two rats of control groups and 2, 4 and 8 rats of experimental groups were sacrificed 20th, 40th and 60th days and each hepatic tissue was observed by the light and electron microscopes. The results were summarized as follows: Light microscopically, hepatocytes of experimental group showed mild inflammatory reactions accompanied by Kupffer cell hyperplasia and disarray of hepatic cords. Electron microscopically, mitochondria showed marked variablity in size and shape with increased distorted cristae as well as increase of matrix densities. Degenerative changes of the cellular organelles participating in protein synthesis and transports were noted, such as dilatation and fragmentation of RER, shedding of ribosomes, increase of free ribosomes, atrophy of Golgi complex, and decrease of SER. Lysosome was not increased but multivesicular lysosomes were occasionally found. From the above results, vitamin A deficiency may specifically alter the morphology of mitochondria and induce multivesicular body formation. Mallory body formation is not noted. Changes on the other endomembranous structures are believed to be secondary.