The genomes of grasses are very different in terms of size, ploidy level and chromosome number. Among them, the Triticeae species (wheat, barley, rye) have some of the largest and complex genomes. Comparative mapping studies between rice, maize, sorghum, barley and wheat have pioneered the field of plant comparative genomics a decade ago. They showed that the linear order (colinearity) of genetic markers and genes is very well conserved opening the way to accelerated map-based cloning and defining rice as a model for grasses. More recently, the availability of BAC libraries and large sets of genomic sequences including the completion of the rice genome have permitted micro-colinearity studies that revealed rearrangements between the grass genomes and provided some insights into mechanisms that have shaped their genome during evolution. This review summarizes a decade of comparative genomics Studies In grasses with a special emphasis on the wheat and barley genomes.