Paramyxoviruses are enveloped viruses containing a non-segmented negative strand RNA genome, and many of them are associated with traditional diseases of childhood and severe disease of humans and animals. In the last two decades, previously unidentified paramyxoviruses have emerged as the cause of serious disease outbreaks in a number of animal species including humans. Hendra and Nipah viruses which recently emerged from their natural fruit bat hosts to infect livestock animals and subsequently man with disastrous consequences are only the latest of a series of novel paramyxoviruses which have emerged to cause disease in livestock and marine animal species. The genetic characterization not only of disease-causing paramyxoviruses but also of recently isolated paramyxoviruses not associated with disease and viruses isolated many years ago and provisionally classified as paramyxoviruses, has provided a golden opportunity for systematic and comparative studies of this important group of viruses at a molecular level. The genomic RNA of negative strand RNA viruses serves as a template for the synthesis of mRNA during transcription and the production of antigenome (+) strands during replication. The genome organization and the structure are highly conserved among this class of viruses. In this review, we will discuss a novel strategy for the rapid characterization of genomes of novel paramyxoviruses and summarize some of the interesting and startling genomic features that our studies have revealed. These include a much wider range of genome sizes than previously acknowledged for members of the Paramyxoviridae, novel genome terminal sequences and intergenic regions, the presence of extensive non-translated regions in certain members of this ever increasing virus family, novel coding patterns of the P gene and the use of different nucleotides for transcription initiation. The molecular studies described provide fresh insight into paramyxovirus genome diversity and evolution.