<jats:p>The major trypsin inhibitor from seeds of Jobs' tears (<jats:italic>Coix lachryma‐jobi</jats:italic>) was purified by heat treatment, fractional precipitation with (NH<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub>SO<jats:sub>4</jats:sub>, ion‐exchange chromatography on DEAE‐Sepharose, gel‐filtration on Sephadex G‐75 and preparative reverse‐phase HPLC. The complete amino acid sequence was determined by analysis of peptides derived from the reduced and <jats:italic>S</jats:italic>‐carboxymethylated protein by digestion with trypsin, chymotrypsin and the <jats:italic>S. aureus</jats:italic> V8 protease. The polypeptide contained 64 amino acids with a high content of cysteine. The sequence exhibited strong homology with a number of Bowman‐Birk inhibitors from legume seeds and similar proteins recently isolated from wheat and rice.