Leaves of Streptocarpus Constant Nymph have been irradiated with X-rays and fast neutrons. Considering the production of plantlets on the rooted leaf-halves as well as the frequency of mutants among them, the optimal dose for X-rays was found to be 3 krad. Like Saintpaulia ionantha, Streptocarpus produces solid mutants after irradiation, a fact which indicates that each plantlet, developing from an adventitious bud, originates from only one cell. Moreover, a high mutation frequency has been observed as well as a wide variability among the 857 mutants obtained. Application of a heavy X-ray dose (4–5 krad) a few days after colchicine treatment resulted in a frequency of tetraploids which was twice the one obtained after colchicine treatment alone. A number of mutants and (auto)tetraploids have been propagated and tested for their commercial value. Sofar, 5 mutants have been commercialized, viz. Purple Nymph, Mini Nymph, Blue Nymph, Netta Nymph and Cobalt Nymph.