Restriction fragment length polymorphisms (RFLPs) demonstrating X-linked inheritance have been identified for proteolipid protein (PLP) and thyroxine-binding globulin (TBG) in sheep. Genetic linkage between ovine PLP and TBG was examined in a three-generation flock containing 122 individuals. Significant linkage between the loci was observed with a combined lod score of 7.48 at a recombination fraction of 5 cM.