In this article I review research undertaken over the past 30 years into the role that gene duplication played in shaping vertebrate genomes. I discuss early karyotype studies that pointed to a relative stability of mammalian and avian genomes, the discovery and possible evolutionary significance of enormous genomes in urodele amphibians and lungfish, genome compaction in certain specialised bony fish, evidence for two rounds of total genome doubling in early vertebrate evolution and the fate of duplicated genes in polyploid fish.