Conflicting results have been reported concerning the phenotypes of collagen produced by cultured Ito cells. These variations may be attributed to differences in pretreatment, i.e., with or without vitamin A to facilitate the separation of Ito cells. In the present study, the effects of vitamin A on collagen metabolism by Ito cells and hepatocytes of rats were analyzed. In cultured Ito cells, staining reactions to type I collagen increased, and those to type IV collagen and laminin decreased after pretreatment with vitamin A. The rate of collagen synthesis by Ito cells decreases significantly by treatment with vitamin A. The decrease was clearer in degraded collagen than in intact collagen. The synthesis of type I collagen increased and that of type IV collagen significantly decreased in Ito cells by treatment with vitamin A. In the hepatocytes, the staining reaction to type I collagen increased with vitamin A pretreatment. The net collagen and type III collagen synthesis in hepatocytes decreased by treatment with vitamin A. These results indicate that vitamin A modifies collagen metabolism in different cell types in different ways.