Abstract Evidence has been presented for the presence of a phenolic substance which has not been previously reported in sorghum seedlings. The substance is similar to p -hydroxymandelonitrile-β-glucose in that it is derived from D -glucose and L -tyrosine. However, glucose is not released when the material is treated with β-glucosidase although hydrolysis with 1 N H 2 SO 4 for 15 min at 100°C releases glucose and an aromatic compound which reduces silver ions under alkaline conditions. The phenolic material is also different from p -hydroxymandelonitrile-β-glucose in that it reacts with acidic 2,4-dinitrophenylhydrazine to form a 2,4-dinitrophenylhydrazone.The maximum absorption of the 2,4-dinitrophenylhydrazone is at 370 mμ. When seedlings metabolized DL -tyrosine-2- 14 C the hydrazone isolated contained 14 C. Furthermore the relative specific activity of the 2,4-dinitrophenylhydrazone derived from this phenolic substance was approximately the same when the seedlings metabolized DL -tyrosine-2- 14 C, DL -tyrosine-3- 14 C, L -tyrosine-U- 14 C or D -glucose-U- 14 C. It is suggested the substance may be a precursor of p -hydroxymandelonitrile-β-glucose.