The relationship between the electrophoretic mobility at pH2.1 of dansyl-glycopeptides of known composition and their molecular weight is shown to conform with a model equation previously derived for peptides. A dansyl-glycopeptide prepared from hen's-egg ovotransferrin is degraded sequentially with two glycosidases. The molecular weight of each glycopeptide intermediate formed is determined from its electrophoretic mobility. From successive molecular-weight changes, the number and type of sugar residues lost from the parent glycopeptide can be decided and the probable composition of each intermediate determined. The notion that the method has considerable application and would permit analysis of very small quantities of glycopeptides is discussed.