The procedures for preparing a food material with antihypertensive efficacy from sardine muscle have been reviewed. Hydrolysis of sardine muscle by pepsin yielded angiotensin I-converting enzyme (ACE)-inhibitory peptides. Further studies aimed at preparing a hydrolyzate with potent ACE-inhibitory activity as well as having good flavor were carried out using Bacillus licheniformis alkaline protease. After 17h of hydrolysis of 0.3wt% sardine protein, the 10wt% ethanol fraction obtained with ODS resin showed some excellent properties, including strong ACE-inhibitory activity (IC₅₀=0.015mg protein/mL), high digestive resistance, no bitterness, and no antigenicity. In addition, this fraction was confirmed to have a significant in vivo depressor effect in mildly hypertensive volunteers ( n =29), who showed a 9.3mmHg reduction in systolic blood pressure and 5.2mmHg reduction in diastolic blood pressure after 4 weeks of oral administration of this peptide drink (4g of the ODS fraction/200mL/day).