Temperature-sensitive mutants of vesicular stomatitis virus were examined for their ability to synthesize intracellular virus-specific RNA species at the nonpermissive temperature. Four mutants from complementation group I (ts 11, ts 12, ts 13, ts 114) were compared to two mutants from complementation group IV (ts 41, ts 44). Mutants within one group did not resemble each other in their phenotypes; nevertheless, two distinct pathways of RNA synthesis were detected: one for transcription and the other for replication.