This paper discusses how the fluorescence from semiconductors might be useful in constructing an opticalmaser. Attention is given to the sharp line emission which occurs at low temperatures in CdS and whicharises from excitons bound to impurities. Some recent experimental results are summarized which giveinformation concerning the fluorescent efficiency and the depth to which crystals are excited using ultravioletlight for excitation. Possible maser geometries are discussed and the opportunities for using an evacuatedground state are pointed out. There appear to be several severe difficulties in the way of success. Theseare partly associated with the small depth of penetration of the exciting light, with the low fluorescent efficienciesavailable and with the inability to grow large perfect crystals with controlled impurity content. Animprovement in the art of crystal growing is probably necessary before the effects described here can beexpected to result in a useful optical maser.