Angiotensin I that converts the enzyme (ACE) inhibitory peptide, Gly-Pro-Leu, previously purified and identified from the Alaskan pollack skin gelatin hydrolysate, were synthesized. In addition, the peptides Gly-Leu-Pro, Leu- Gly-Pro, Leu-Pro-Gly, Pro-Gly-Leu, Pro-Leu-Gly, Gly- Pro, and Pro-Leu, which consisted of glycine, proline, and leucine, were synthesized by the solid-phase method. The IC50 values of each tripeptide . namely Leu-Gly-Pro, Gly- Leu-Pro, Gly-Pro-Leu, Pro-Leu-Gly, Leu-Pro-Gly, and Pro-Gly-Leu . were 0.72, 1.62, 2.65, 4.74, 5.73, and 13.93 ¥ìM, respectively. The ACE inhibitory activity of these tripeptides was higher than that of dipeptides, such as Gly- Pro and Pro-Leu with IC50 values of 252.6 and 337.3 ¥ìM, respectively. Among the tripeptides, Leu-Gly-Pro and Gly- Leu-Pro had higher inhibitory activity than Gly-Pro-Leu that was isolated from the Alaskan pollack skin gelatin hydrolysate. Among the different types of tripeptides that were examined, the highest ACE inhibitory activity was observed for Leu-Gly-Pro. It had the leucine residue at the N-terminal and proline residue at the C-terminal.