Peptides play an important primary role as a supply of essential amino acids and a source of nitrogen. Recent studies have reported on another role of peptides: having specific amino acid sequences that can express some biological functions in vivo. For an exhaustive study and supply of biologically active peptides, a large-scale screening of protein sources is necessary. Various physiologically functional peptides, such as opioid, immunostimulating, mineral carrier, ACE inhibitory, antihypertensive, and antimicrobial peptides, have been derived from milk protein: both caseins and whey proteins (Meisel, 1998; Korhonen&Pihlanto-Lepp älä , 2001). Milk is known to be a rich source for the supply of bioactive peptides compared to other protein sources such as animal and fish meat, wheat, and soybean proteins. Among the bioactive peptides, ACE inhibitory peptides and antihypertensive peptides have been extensively researched worldwide, because hypertension is a major risk factor in cardiovascular disease, such as heart disease (FitzGerald&Meisel, 2000; Kitts&Weiler, 2003). We discuss the isolation, utilization, and application of bioactive peptides, especially ACE inhibitory peptides and antihypertensive peptides including our recent human studies on their use as a functional food material.