Abstractγ ‐Glutamyl‐S‐methylcysteine has been isolated from extracts of lima beans (Phaseolus lunatus L.). Two further peptides, γ ‐glutamyl‐S‐methylcysteine sulfoxide and γ ‐glutamyl‐leucine have been tentatively identified. In addition, free S‐methylcysteine was found in such extracts. The presence of these constituents in varying amounts was observed in all of 6 other varieties of beans that were investigated. During germination S‐methylcysteine and all peptides occurring in lima beans are metabolized to unknown products. An oxidation‐reduction function during the early phases of growth is suggested for the system: γ ‐glutamyl‐S‐methylcysteine/ γ ‐g