In our previous study, we have proposed a lamellar structure for Ala-Gly repeated copolymeric peptide, a model for crystalline region of Bombyx morisilk fibroin. Here, we propose the structure of (AGSGAG)5with silk II form which is a more mimic of the crystalline region of B. morisilk fibroin than (AG)15. The local structure for each Ala residue was determined from 13C CP/MAS NMR spectra of 10 different [3-13C]Ala-(AGSGAG)5peptides differing in their 13C labeling positions. The highest field peak for the Ala Cβ carbon (16.7 ppm) assigned to a distorted β-turn structure and/or random coil changes significantly depending on the 13C labeling position. In addition, the fractions of the random coil and/or distorted β-turn component of each Ser residue were determined by REDOR experiments from the 13C−15N atomic distances of five versions of the above peptide with different [1-13C]Gly-Ser-[15N]Gly positions. By combining the structural information of Ala and Ser residues from solid state NMR, with statistical mechanical calculation previously used for (AG)15, the probable lamellar structures of (AGSGAG)5in the solid state are proposed. The models of two turns in the central part of the sequence of (AGSGAG)5consist of approximately 8−12 amino acids. The effect of the introduction of Ser residue on the local structure of Ala-Gly copolymeric peptides is also discussed on the basis of the evidence from 13C solid state spin−lattice relaxation experiments.