Estimation of the arginine content of germinating seeds of Vicia faba, Canazalia ensiformis, Phaseolus vulgaris and Pisum sativum, showed a lowering in concentration during the first week of germination. When [14C] arginine was fed to cotyledon discs of Vicia faba, ornithine, proline, urea and carbon dioxide quickly became labelled and other amino acids became labelled after a longer period of incubation. Arginase was extracted from the V. faba and shown to be present in the roots, shoots and cotyledons during the first 6 days of germination. Urease was also extracted from V. faba and shown to have a pH optimum of 8.0 for extraction. The possible presence of an ornithine cycle is discussed.