Well-defined (glyco)peptide-containing block copolymers were synthesized by ring-opening polymerization of L-phenylalanine N-carboxyanhydride (NCA) (2), gamma-benzyl-L-glutamate NCA (3), and O-(tetra-O-acetyl-beta-D-glucopyranosyl)-L-serine NCA (6) initiated with omega-amine-terminated poly(2-methyl-2-oxazoline) (la) and poly(2-phenyl-2-oxazoline) (Ib) macroinitiators in dichloromethane at 27 degrees C. <(DP)over bar s> of peptide segments of the resulting poly(2-methyl-2-oxazoline)-block poly(L-phenylalanine) (4), poly(2-methyl-2-oxazoline)-block-poly(gamma-benzyl-L-glutamate) (5a), poly(2-methyl-2-oxazoline)-block-poly[O-(tetra-O-acetyl-beta-D-glucopyranosyl)-L-serine] (7a), and poly(2-phenyl-2-oxazoline)-block-poly[O-(tetra-O-acetyl-beta-D-glucopyranosyl)-L-serine] (7b) were close to monomer/macroinitiator feed molar ratios. On the other hand, the 3/1b system gave a block copolymer having a longer peptide chain, compared to the calculated value. The factor for controlling chain lengths of the (glyco)peptide blocks was discussed in connection with the side reaction of NCA polymerization, i.e., production of hydantoic acid. Furthermore, glycopeptide-bearing block copolymers, poly(2-methyl-2-oxazoline)-block-poly[O-(beta-D-glucopyranosyl)-L-serine] (8a) and poly(2-phenyl-2-oxazoline)-block-poly[O-(beta-D-glucopyranosyl)-L-serine] (8b), were derived from 7a and 7b, respectively, by deacetylation with hydrazine monohydrate.