Type IV (alpha 1 and alpha 2 chains) appears to be the only procollagen present in basement membranes. The structure of this protein is highly divergent from the interstitial and type V procollagens as exemplified by the interruptions in the Gly-X-Y region and unprocessed amino and carboxyl noncollagenous peptides. To expand our knowledge concerning the primary sequence of type IV and to investigate the factors influencing its unique distribution, we recently isolated cDNA clones coding for part of the human alpha 1(IV) chain. To determine if the alpha 1(IV) gene was cytologically linked to other procollagen genes that have been assigned to autosomes 17, 12, 7, and 2, overlapping clones covering 2.6 kilobases (kb) of the alpha 1(IV) mRNA were used together for in situ hybridization to human metaphase chromosomes. Here, we show precise localization of alpha 1(IV) at the telomere of 13q, thereby defining a fifth chromosome that contains members of this large and surprisingly dispersed multigene family.