Clinical studies have demonstrated a beneficial effect on blood pressure for milk derived material containing isoleucyl-prolyl-proline (IPP) and valine-prolyl-proline (VPP) peptides. The aim of the present study was to evaluate the blood pressure lowering effect of three different IPP and VPP doses in products with a comparable electrolyte and protein composition. The present study was designed as a randomized, double-blind, parallel-group, dose-response trial: 166 subjects (>140/90 mmHg) received placebo during a 2-week run-in, 8-weeks intervention followed by a 2-week washout. Results indicate that materials containing IPP and VPP do lower blood pressure dose-dependently (p < 0.05 for diastolic blood pressure, DBP). The effect on systolic blood pressure (SBP)/DBP over 8 weeks compared with placebo was + 0.1/- 1.3, - 1.5/- 1.4 and - 2.5/- 1.9 mmHg for the low, medium and high dose of peptides, respectively. The percentages of subjects who showed a fall in SBP > 3 mmHg or who attained an SBP below 140 mmHg, were 54% (placebo), 64% (low), 76% (medium) and 71% (high dose) respectively. This effect can only be demonstrated for office pressure and not for home or ambulatory pressure. Furthermore, the results suggest that the magnitude of the fall in blood pressure is a function of baseline blood pressure. We conclude that IPP and VPP may have a modest dose-dependent effect on office blood pressure in mildly hypertensive subjects although this could not be confirmed with ambulatory or home blood pressure measurements.