Although all of the over 200 patients treated with NCT have been irradiated by reactor-produced neutrons, in the present climate of public opinion one cannot expect the routine use of nuclear reactors in hospitals or clinics to be tolerated. While there are several other methods of producing neutrons in the necessary quantities, the Paul Scherrer Institute (PSI) is very well placed to develop techniques base don spallation, in which a beam of protons hits a production target of some convenient material such as tungsten. Because spallation produces neutrons of very similar energies to reactors, the problem of moderating them to keV energies is rather similar. However, there is an additional component of high-energy neutrons, whose intensity depends on the energy of the initial beam, which has to be taken into account in any practical design. Simulations using the well-known codes LAHET, MCNP and GEANT show that a 100 (mu) A beam of 72 MeV protons, well within the capabilities of PSI, could produce enough keV neutrons for therapy.