Restriction-fragment-length polymorphisms (RFLPs) of the sarcomeric- myosin heavy chain multigene family were studied in 13 populations of 4 chromosomal species (2n = 52, 54, 58 and 60) of the mole rat Spalar ehrenbergi superspecies in Israel. A minimum number of 6 hybridizing fragments occurred in the mole rat, corresponding to a minimum of 6, probably even 8, different loci of the sarcomeric myosin heavy chain. The level of polymorphism was≈ 31%, with a low number of alleles in the polymorphic loci. All of the populations, including a desert isolate, were polymorphic at some level. Among- sample fragment variation was adequate to differentiate between some of the chromosomal species, and confirms earlier evidence that gene flow between the chromosomal species is limited.