It is suggested that rust resistance in wheat may be due to the liberation of phenols in the host-cell upon the entrance of the fungus. A tentative method has been developed for determining phenolic compounds in wheat press-juice, including a critical study of the conditions for clarifying the juice with tungstic acid. The content of phenolic substances in wheat varieties has been found to bear some relation to rust resistance. Yellow pigments of the flavone type appear to be the main phenolic compounds present, and these are being investigated.