Nonenergy applications of fusion reactors are considered. The direct use of the 14.7-MeV protons from the D-3He reaction for the production of positron-emitting isotopes for medical, industrial, and scientific uses is explored in some detail. Inside a working D-3He reactor, the 14.7-MeV proton flux is of the order of 1022 cm2/s. The conversion of fertile nuclei to useful nuclei can be very prolific. Since the value of such isotopes can be very high (approximately $1012/g), it is possible to have an economical reactor for a machine that just breaks even or is even below breakeven in energy terms. Existing research devices can produce interesting quantities of isotopes for experimental and demonstration purposes. A major problem is the development of a demand for the large quantities of positron emitters that could be produced. If such a source of isotopes were to exist, as with many new developments, the demand would probably follow.