The cardiovascular protective effects of the traditional Chinese medicine Bak Foong Pills (BFP) were investigated. Spontaneously hypertensive rats (SHR) were treated (3 g/kg) over a 5-month period and blood pressure measurements periodically tested with a plethysmographic tail cuff. Following treatment, blood samples were analysed for serum electrolyte levels and lipid levels and brain tissue subjected to micro-array analysis. In vitro experiments were also conducted to identify possible direct vasorelaxatory effect. The results showed that BFP was able to significantly reduce both systolic and diastolic blood pressure by about 30 mmHg in SHR following 5 months of treatment, when compared to untreated animals. Investigation for possible mechanisms of actions revealed that BFP treated rats had elevated blood serum K(+) levels, and also demonstrated decreased serum triglyceride levels. Micro-array analysis of brain tissue showed altered expression of acetylcholine and lysosphingolipid receptor genes that are known to regulate blood pressure. In vitro experiments also showed that BFP caused a concentration-dependant vasorelaxation of isolated rat aortae when contracted with phenylepherine, which was partially inhibited by nitric oxide synthase inhibitor L-NAME (100 microM). These data suggest that BFP is able to significantly reduce hypertension in SHR through mechanisms probably involving a combination of increased serum K(+), vasorelaxatory action, reduced serum triglyceride and altered gene regulation in the higher centres.