Important methods to artificially induce mutations are the use of chemical and physical agents. Most chemical mutagens are alkylating agents and azides. Physical mutagens include electromagnetic radiation, such as γ rays, X rays, and UV light, and particle radiation, such as fast and thermal neutrons, β and α particles. Mutagenic treatment of seeds is the most convenient and, therefore, the standard method in seed propagated crops. Seeds can be treated in large quantities and are easily handled, stored, and shipped. It is fairly easy to repeat the conditions of mutagenic treatment, pre- and post-treatment, and hence, to obtain reproducible results within practical limits. Besides seed treatment, whole plants, cuttings, tubers, pollen, bulbs, corms, or in vitro plants or tissues can be treated. This chapter is restricted to the commonly applied techniques of mutation induction in seeds by ethyl methanesulfonate (EMS) treatment and by γ and fast neutron irradiation.