A novel family of tandemly repeated DNA in the cereal genome, "Spelt1," was isolated and described. This family accounts for about 2% of the DNA of Aegilops speltoides, one of the putative donors of B genome of hexaploid wheat. Genomes of fifteen other cereal species studied, including those with AB, AG, and ABD genome formulas, contain significantly lower amounts of Spelt1 repeats. RFLP analysis revealed three different types of Spelt1 sequence organization in the wheat and aegilops genomes studied. Data indicating that Spelt1 is a specific marker of Ae. speltoides-chromosomes are presented.