A procedure for the isolation and sequence analysis of the "fast" avenin component (N9) from the oat (Avena sativa L., cv. Narymsky 943) is described. Component N9 was prepared by an ion-exchange high-performance liquid chromatography on a strong cation exchange column type Mono S (Pharmacia, Sweden) in 4 M urea, pH 3.5, with a linear gradient of NaCl. A polypeptide chain of avenin N9 was reconstructed by the CNBr and tryptic peptides on a model 470A protein gas-phase sequencer (Applied Biosystems, USA). A good yield of tryptic peptides were obtained by an enzymatic hydrolysis of avenin N9 preliminary immobilized on Thiopropyl-Sepharose 6B (Pharmacia, Sweden) at cysteine residues. Avenin N9 consists of 182 amino acid residues end exhibits the features common for all the known prolamins.