NC1, the C‐terminal non‐collagenous globular domain of collagen IV, represents one of the two end regions responsible for the assembly and cross‐linking of the extracellular network of basement membrane collagen. Several cDNA clones for the NC1 domain of the α1(IV) collagen chain of mouse have been isolated by using synthetic oligonucleotides as screening probes for mouse libraries. The oligonucleotides were synthesized according to known stretches of the corresponding protein sequence. Sequencing of the overlapping cDNA clones allowed the complete amino acid sequence of the NC1 domain to be deduced as well as the C‐terminal 165 amino acid residues of the triple helix. It consists of 229 amino acid residues which comprise two homologous regions with a high content of cysteine. These DNA and protein sequences are compared to the corresponding sequences of other collagens and discussed with respect to their structural and biological significance.