A genetic map of diploid wheat, Triticum monococcum L., involving 335 markers, including RFLP DNA markers, isozymes, seed storage proteins, rRNA, and morphological loci, is reported. T. monococcum and barley linkage groups are remarkably conserved. They differ by a reciprocal translocation involving the long arms of chromosomes 4 and 5, and paracentric inversions in the long arm of chromosomes 1 and 4; the latter is in a segment of chromosome arm 4L translocated to 5L in T. monococcum. The order of the markers in the inverted segments in the T. monococcum genome is the same as in the B and D genomes of T. aestivum L. The T. monococcum map differs from the barley maps in the distribution of recombination within chromosomes. The major 5S rRNA loci were mapped on the short arms of T. monococcum chromosomes 1 and 5 and the long arms of barley chromosomes 2 and 3. Since these chromosome arms are colinear, the major 5S rRNA loci must be subjected to positional changes in the evolving Triticeae genome that do not perturb chromosome colinearity. The positional changes of the major 5S rRNA loci in Triticeae genomes are analogous to those of the 18S-5.8S-26S rRNA loci.