The N-terminal procollagen peptide of the pN alpha 1(I) chain from dermatosparactic calf skin contains 139 amino acid residues. For the determination of the amino acid sequence the procollagen peptide was treated with pyroglutamate aminopeptidase, protease from Staphylococcus aureus V8 and trypsin. The fragments obtained were separated by molecular sieve and ion-exchange chromatography and submitted to automated Edman degradation. The procollagen peptide consists of three segments, an N-terminal globular domain which contains all the cysteine residues and most of the hydrophobic residues present in the entire peptide, a triple helical part with a relatively high content of proline and hydroxyproline, and a short nonhelical region which forms the connection to the nonhelical region of the alpha 1(I) chain and which contains the proline-glutamine bond specifically split by the N-terminal procollagen peptidase during conversion of procollagen to collagen.