Caveolin is a protein present in membrane specializations termed caveolae where it may play a structural role. Previous studies on the cDNA sequence of chicken caveolin demonstrated that it is an integral membrane protein without significant homology to any known protein. The cDNA sequence of human lung caveolin is presented here. A striking sequence homology is observed with the chicken protein, as well as a very recently reported protein termed VIP21 [(1992) J. Cell Biol. 118, 1003-1014], a putative vesicle transport protein isolated from MDCK cells. Genomic Southern blots suggest that caveolin is present in a single copy, and Northern blots confirm that the caveolin mRNA is elevated in muscle.