Summary.By using seven endonucleases and four bovine cDNA probes specific for αs1‐,αs2‐,ß‐, and K‐casein genes, nine restriction fragment length polymorphisms (RFLPs) have been found in the sheep orthologous DNA regions. In contrast to the low level of variation observed at the protein level, these DNA polymorphisms determine a high level of heterozygosity and, therefore, represent useful tools for genetic analyses since they can also be obtained without the need for gene expression. In fact, informative matings suggest that in sheep, as in cattle, the four loci