The ten double-stranded RNA segments of the reovirus genome are not transcribed at equal frequencies until later times during the course of infection. When an inhibitor of protein synthesis such as cycloheximide was added to infected cells at the beginning of infection, only four of the ten segments were transcribed. By two hr post infection, five and possibly seven of the segments were being transcribed. By four hr post infection all ten segments were being transcribed but not yet at equal relative frequencies. The transcription pattern at intermediate (4 hr) and late (10 hr) times were verified without using cycloheximide. A repressor present in the host cell may be responsible for controlling transcription of the reovirus genome.