D manufactures and sells home video tape recorders. P owns the copyrights on some of the television programs that are broadcast on the public airwaves. The general public uses video tape recorders sold by P to record some of these broadcasts, as well as a large number of other broadcasts. P commenced this copyright infringement action against D. P alleged that some individuals had used Betamax video tape recorders (VTR's) to record P's copyrighted works which had been exhibited on commercially sponsored television and contended that these individuals had thereby infringed P's' copyrights. P maintains that D is liable for the copyright infringement committed by Betamax consumers because of P's marketing of the Betamax VTR's. P sought money damages and an equitable accounting of profits from D, as well as an injunction against the manufacture and marketing of Betamax VTR's. The separate tuner in the Betamax enables it to record a broadcast off one station while the television set is tuned to another channel, permitting the viewer, for example, to watch two simultaneous news broadcasts by watching one 'live' and recording the other for later viewing. Tapes may be reused, and programs that have been recorded may be erased either before or after viewing. A timer in the Betamax can be used to activate and deactivate the equipment at predetermined times, enabling an intended viewer to record programs that are transmitted when he or she is not at home. Thus a person may watch a program at home in the evening even though it was broadcast while the viewer was at work during the afternoon. The Betamax is also equipped with a pause button and a fast-forward control. The pause button, when depressed, deactivates the recorder until it is released, thus enabling a viewer to omit a commercial advertisement from the recording, provided, of course, that the viewer is present when the program is recorded. The District Court denied P all relief. The Court of Appeals reversed holding D liable for contributory infringement. The Supreme Court granted certiorari. The average member of the public uses a VTR principally to record a program he cannot view as it is being televised and then to watch it once at a later time. This practice, known as 'time-shifting,' enlarges the television viewing audience. For that reason, a significant amount of television programming may be used in this manner without objection from the owners of the copyrights on the programs.