To study the molecular biology of eye development, cDNA clones for type IV collagens, the predominant collagen in the lens, are being constructed and identified. Four different cDNA libraries comprising a total of 170,000 individual colonies have been established. These libraries have been screened and counter screened for Type IV cDNA clones with in vitro labelled mRNA from cells and tissues producing or not producing Type IV collagen and at low stringency with collagen Type I specific cDNA probes. Twenty-nine prospective Type IV collagen cDNA colonies have been selected from among the 170,000 colonies. Among the positively identified clones, 3 cDNA clones code for 18S rRNA, 3 cDNA clones code for 28S rRNA, and 5 clones code for Type I collagen. Since no cDNA clones coding for the COOH end of Type I collagen from mouse have been reported, one of these clones is now being sequenced and characterized. Primer extension experiments using synthetic oligo-nucleotides complementary to 14 nucleotides of deduced sequence for Type IV collagen mRNA suggest that Type IV collagen and ribosomal RNA share short regions of homology. The biological significance of this interesting finding is not yet known. The other putative Type IV collagen clones are being sequenced in order to positively identify and characterize Type IV collagen cDNA clones.