From fifth symposium on engineering problems of fusion research; Princeton, New Jersey, USA (6 Nov 1973). The development of neutral injectors at ORNL has stressed input power levels sufficient to heat plasma ions. It has also stressed other problems equally important for success in neutral-injection heating. Injection pulse lengths, which have been extended to 200 msec, will need to be extended further for tokamaks of the future. This requires the ORNL approach of energyefficiency, cooled ion sources, and dc supplies. Low bcam impurity content requires high duty--cycle cleanup, which again means energy efficiency, cooled sources, and dc supplies. Design of the injectors to have gas efficiency and to have sufficient auxiliary pumping is necessary to keep cold gas streaming down to levels not expected to perturb the tokamak plasma. (auth)