Tomato seeds deficient in most of the elements known to be essential for higher plants were tested for their sensitivity to gamma radiation. In the first generation leaf length was used as an index of radiation sensitivity: zinc deficient seeds were much more radiosensitive than controls, as to a lesser extent were seeds deficient in copper, molybdenum and sulphur. In the second generation, the spectrum of mutations produced from irradiated deficient seeds was compared with that from irradiated controls. Pale green cotyledon mutants were significantly more frequent from manganese-deficient seeds, and much less frequent from zinc-deficient seeds; a low yield of mutants was found from seeds deficient in magnesium and boron.