Protease inhibitor activity was determined for a wide range of differing field bean (Viciu fabn) varieties and genotypes. Although a two-fold variation was observed under the assay conditions used, the highest values were approximately five times less active in inhibiting trypsin than either soya or navy beans. N o correlation was found between protein content and protease inhibitor activity. Water extracts from the testa from coloured-flower varieties inhibited the activity of a-amylase, lipase and trypsin. The addition of polyvinylpyrrolidone reactivated these enzymes t o varying degrees. No inhibitory activity was found in similar extracts from white-flowered varieties. It was concluded that the enzyme inhibition exhibited by extracts of the seed coat of coloured varieties was due to the presence of tannins.