Identical measles viral mRNA species were present in similar amounts in the persistently infected cell lines LU106, HEpPi and MaSSPE, and in lytically infected cells as determined from Northern blots. The attenuation of transcription with the gene order did not vary significantly between different infected systems. A previously described selective restriction of F protein production in Lu106 cell could not be explained by defective transcription of F mRNA. RNA synthesis also continued unimpeded at restrictive temperatures for the temperature-sensitive viruses in Lu106 and HEpPi cells. Northern blotting revealed a prominent band in HEpPi RNA and a weak band in Lu106 RNA with the characteristics of incomplete genomes. In all infected cells, previously unrecognized small RNA species, hybridizing with the F- and H-specific probes, were discovered.