Basement membrane zone gene expression by fibroblast cultures, established from individuals varying in age from 14 fetal weeks to 61 years, was examined by molecular hybridizations with human sequence specific cDNAs corresponding to type IV procollagen and laminin subunit polypeptides. Northern transfer analysis with poly(A)+RNA revealed the presence of specific mRNA transcripts for alpha 1(IV) and alpha 2(IV) chains of type IV procollagen as well as B1 and B2 chains of laminin. Laminin A chain mRNAs were not detected using the same RNA preparations. Quantitative estimates of the steady-state levels of type IV procollagen and laminin mRNAs indicated that they were of relatively low abundance, as compared with mRNA to type I procollagen. The expression of alpha 1(IV) and alpha 2(IV) collagen genes was high in fetal fibroblasts but was reduced to low, yet detectable, levels in cultures established from 3-d to 61-year-old individuals. In contrast, the laminin B1 and B2 chain mRNA levels showed little age-associated variation within the cultures examined. These results provide evidence for differential regulation of the expression of different basement membrane zone macromolecules during chronologic aging.