Latent transforming growth factor beta 1-binding protein (LTBP1) is an important component of the large latent TGF-beta 1 complex. It plays a role in the assembly and secretion of the latent TGF-beta 1. In this paper we have used a cDNA probe for LTBP1 to determine the chromosomal localization of the human gene. Using a panel of well-defined human x rodent somatic cell hybrid lines, LTBP1 could be assigned to chromosome 2. Further sublocalization of the gene to 2p12-->q22 was achieved using three hybrid lines which contain partially over-lapping fragments of chromosome 2.