Tropomyosins are a group of actin-binding proteins expressed as different isoforms in muscle and non-muscle cells. Two tropomyosin loci have already been mapped in the mouse genome, on Chromosomes (Chrs) 6 and 9. By using a human cDNA fragment of tropomyosin non-muscle isoform (TPM3) gene that maps on human Chr 1q, and a mapping panel from a murine interspecific cross, we mapped nine distinct tropomyosin-related loci in the mouse genome, on seven different chromosomes: Chrs 3, 4, 6, 7, 14, 17, and X.