The identification and clinical significance of light microscopic giant mitochondria (GM) were investigated in liver biopsy specimens of 60 alcoholics. By light microscopic examinations using the same section and neighboring sections, we suggest that light microscopic GM correspond to the crystalloid bodies (CB) detected on ultrastructural observation. The reasons are as follows: (1) difference in stainability between eosinophilic light microscopic GM and acidbasophilic mitochondria; (2) similarity in morphological features and density of the round- and cigar-shaped types at the light microscopic level to those of CB at the electron microscopic level; (3) similarity of the area occupied in the hepatic cytoplasm at both light and electron microscopic levels; (4) the crystalline structure of CB in compatible with the subtype of Mallory body (MB); (5) a description of CB has been made at the electron microscopic level, although not yet at the light microscopic level. Moreover, we clinically observed that light microscopic GM seldom appeared either in early fatty liver of cases aged 35 or less or the late macronodular liver cirrhosis stage of alcoholic liver injuries while they were frequently recognized during the acute aggravation phase of the chronic stage (GPT: p less than 0.05). Furthermore, if one was to assume that MB is a change accompanying necrosis of the liver cells, the light microscopic GM might be a change accompanying degeneration of the cytoplasmic organelles.