We have reconstructed a molecular genetic history of human annexins to chronicle their origins and dispersal throughout the genome. This involved the completion of chromosomal mapping, determination of ancestral relationships, and estimation of gene duplication dates. Fluorescence in situ hybridization localized human annexin XI (ANX11) to 10q22.3-q23.1 and annexin XIII (ANX13) to 8q24.1-q24.2. Orthologous annexins showed minor rate variation when calibrated to species separation times given by the fossil record, but paralogous subfamilies have diverged at fivefold variable rates. The rates and extents of sequence divergence were used to predict a mean separation time of 450 million years between vertebrate annexins, although their common ancestor may have emanated from invertebrate stock. Annexins XIII and VII formed a phylogenetically early clade, and annexins II and VIa were the most divergent members of two distinct clades. ANX6 may have been created by tandem duplication about 500 million years ago (Mya) and duplicated again to form ANX5 400 Mya, whereas ANX4 and ANX8 are proposed to be sequential duplication products from annexin XI. Vertebrate annexins thus proliferated via a cascade of gene duplications in higher metazoa to form at least three diverging groups of ubiquitous and structurally related genes. These can be distinguished by their dispersed genomic locations as well as their individual patterns of expression and partially differentiated functions.