Rapeseed protein isolate (RPI) was hydrolyzed with Alcalase followed by reverse-phase high performance liquid chromatography (RP-HPLC) purification of bioactive peptides. The rapeseed protein hydrolysate (RPH) obtained after 4h digestion with Alcalase had a degree of hydrolysis (DH) of ~11%. Gel permeation chromatography separation showed high contents of low molecular weight peptides in the RPH when compared to the RPI. After preparative and analytical RP-HPLC separations, three peptides (LY, TF and RALP) were purified and amino acid sequence determined by tandem mass spectrometry. LY (IC50, 0.11mM) was the most potent (p<0.05) against ACE activity when compared to TF (IC50, 0.81mM) and RALP (IC50, 0.65mM). However, RALP (IC50, 0.97mM) was the most potent (p<0.05) against renin activity when compared to LY (IC50, 1.87mM) and TF (IC50, 3.1mM). Single oral administration (30mg/kg body weight) to spontaneously hypertensive rats showed LY and RALP to be the more effective hypotensive agents with maximum blood pressure reduction of -26 and 16mmHg, respectively when compared to TF (-12mmHg). The results suggest that the higher number of hydrophobic amino acid residues LY and RALP contributed to their higher in vitro and in vivo activities when compared to TF.