The present invention relates, in general, to a methodology for the generation or nonsegmented negative-strand RNA viruses (Pringle, 1991) from cloned deoxyribonucleic acid (cDNA). Such rescued viruses are suitable for use as vaccines, or alternatively, as plasmids in somatic gene therapy applications. The invention also relates to cDNA molecules suitable as tools in this methodology and to helper cell lines allowing the direct rescue of such viruses. Measles virus (MV) is used as a model for other representatives of the Mononegavirales, in particular the family Paramyxoviridae.