Recent evidence suggests that at least a part of the polyunsaturated fatty acids (PUFAs) heart protective effect is mediated by a relatively small but significant decrease in blood pressure level. We retrospectively evaluated the long-term effect of a PUFA supplementation on the blood pressure level of 111 hypertriglyceridemic subjects with untreated normal-high blood pressure that were prescribed a 2 grams PUFA supplementation in order to improve their plasma lipid pattern. After 12 months of treatment, systolic blood pressure (SBP) meanly decreased by 2.7 +/- 2.5 mmHg (p = 0.001) and diastolic blood pressure (DBP) by 1.3 +/- 3.3 mmHg (p < 0.001), while basal heart rate decreased by 4.0 +/- 4.4 bpm (p < 0.001). Both SBP and DBP reduction were significantly related to the baseline SBP (p < 0.001) and DBP (p < 0.001), respectively. Diastolic blood pressure change was also inversely related to the patient's age (p = 0.004). No significant difference was perceived in the metabolic syndrome subgroup. In our retrospective study, highly purified omega-3 PUFA long-term supplementation is associated with a significant reduction in SBP, DBP, Pulse pressure (PP), and basal heart rate in hypertriglyceridemic patients with normal-high blood pressure. No significant difference was perceived in the metabolic syndrome subgroup. The main determinants of the PUFA anti-hypertensive effect appear to be the basal blood pressure level and age.