What justifies the size of this compendium of reviews on the paramyxoviruses? As intracellular parasites that reproduce with almost complete indifference to nuclear activities, paramyxoviruses have not been providing insights about genes that regulate cellular activities and development, topics that account for much of the excitement in modem biology. For contributions of virus research to those topics, we must look to the retroviruses, which have the propensity to steal developmentally important genes and subvert them to malignant pur- poses, and to the nuclear DNA viruses, whose gene...