Abstract The peptides, (Ala–Lys–Gly)10–Phe, (Ile–Lys–Gly)3–Phe, and (Ile–Lys–Gly)5–Phe, were synthesized by solid-phase fragment condensation method. The contaminating shorter peptides and branched chain peptides were removed by CM-cellulose column chromatography. The peptides were useful as synthetic model substrates for collagen lysyl hydroxylase. The –Ile–Lys–Gly– units in (Ile–Lys–Gly)5–Phe showed a higher affinity to the enzyme than those in (Ile–Lys–Gly)3–Phe. A strong substrate inhibition was observed with highly basic peptide, (Ala–Lys–Gly)10–Phe.