It is intended to provide ACE inhibitory tripeptideswhich are not easily digested by digestive enzymes afterbeing orally taken and thus have fewer tendencies to losetheir ACE inhibitory activity in vivo.More specifically, 3 tripeptides having an ACEinhibitory activity and showing a hypotensive effect in ananimal experiment are discovered from a thermolysindigestion product of sesame. These tripeptidesrespectively have amino acid sequences Leu-Ser-Ala,Val-Ile-Tyr and Leu-Val-Tyr and show an angiotensin convertingenzyme inhibitory activity.