Technical Abstract: The 5S gene is the smallest of the four nuclear ribosomal RNA (rRNA) genes in eukaryotes. In some species the gene is part of the regular rRNA tandem array, while in others the gene is dispersed. The 5S rRNA genes of filamentous fungi form a large multigene family of 50 to 100 copies. During the course of our studies on the genomic evolution of filamentous fungi, we found that these genes display varying degrees of divergence from one another, suggesting that they do not evolve in a concerted manner. This pattern is quite unusual because nuclear rRNA genes represent a paradigm of concerted evolution. The purpose of this study was to characterize the patterns of multigene family evolution and evolutionary genomics of 5S rRNA genes in the genomes of representative filamentous fungi. Our studies show that the genes undergo birth-and-death evolution under strong purifying selection. Furthermore, the rate of gene turnover appears to be quite high in these genomes. Because the 5S genes in these species are dispersed across the genome, our findings indicate that the mechanisms controlling the multiplication and movement of 5S genes across the genome are highly dynamic. This is the first case in which these patterns have been described for a large rRNA multigene family. Furthermore it appears that a process resembling retroposition controls 5S rRNA gene amplification, dispersal and integration in the genomes of filamentous fungi.