Content of main glycoprotein fractions was studied in rat blood plasma under conditions of vitamin A avitaminosis and of subnormal consumption of the vitamin. Main protein fractions were estimated simultaneously with relative content of glycoproteins which was calculated per mg of total proteins. Relative content of gamma-glycoproteins was increased in avitaminosis A, which appears to occur due to elevation of gamma-globulin synthesis in response to secondary infection or intoxication, while the level of alpha 1- and alpha 2-glycoproteins was decreased simultaneously as a result of possible impairment of protein glycosylation in liver tissue. Subnormal consumption of retinol did not alter content of many protein fractions in blood, however under these conditions absolute content of alpha 1-, alpha 2- and beta 2-glycoproteins as well as relative content of alpha 2-glycoproteins were decreased, thus leading to increase in relative content of underglycosylated proteins in blood. Vitamin A appears to be essential for biosynthesis of individual but not of total blood glycoproteins.