Objectives　To　investigate　the　effect　on　essential　hypertension　of　the　topical　application　of　TAT-Cu,　Zn-superoxide　dismutase　(TAT-SOD)　at　left　acupoint　Zusanli　(ST　36),　and　to　observe　whether　the　change　of　electrical　potential　difference　(EPD)　can　be　related　to　the　change　of　blood　pressure.　Methods　Sixteen　patients　with　essential　hypertension　and　16　healthy　subjects　were　included　in　the　study.　EPD　between　the　left　acupoints　of　Yanglingquan　(GB　34)　and　Qiuxu　(GB　40)　was　firstly　screened　out　for　the　EPD　detection.　An　intracellular　superoxide　quenching　enzyme,　TAT-SOD,　was　topically　applied　to　the　acupoint　ST　36　within　an　area　of　1　cm(2)　once　a　day,　and　the　influence　on　EPD　was　investigated.　The　dosage　applied　to　TAT-SOD　group　(n=8)　was　0.2　mL　of　3000　U/mL　TAT-SOD　cream　prepared　by　adding　purified　TAT-SOD　to　a　vehicle　cream,　while　placebo　group　(n=8)　used　the　vehicle　cream　instead.　The　left　acupoints　of　Yanglingquan　(GB　34)　and　Qiuxu　(GB　40)　were　selected　for　EPD　measurement　after　comparing　EPD　readings　between　5　acupoints　on　each　of　all　12　meridians.　Results　EPDs　between　the　left　acupoints　of　GB　34　and　GB　40　for　16　patients　of　essential　hypertension　and　16　healthy　subjects　were　44.9　+/-　6.4　and　5.6　+/-　0.9　mV,　respectively.　Daily　application　of　TAT-SOD　for　15　days　at　ST　36　of　essential　hypertension　patients　significantly　decreased　systolic　blood　pressure　(SBP)　and　diastolic　blood　pressure　(DBP)　of　179.6　and　81.5　mm　Hg　to　153.1　and　74.1　mm　Hg,　respectively.　Responding　to　the　change　in　blood　pressure,　EPD　between　the　left　acupoints　of　GB　34　and　GB　40　also　declined　from　44.4　to　22.8　mV　with　the　same　trend.　No　change　was　observed　with　SBP,　DBP　and　EPD　between　the　left　acupoints　of　GB　34　and　GB　40　with　the　daily　application　of　the　placebo　cream.　Conclusion　Enzymatic　scavenging　of　the　intracellular　superoxide　at　ST　36　proved　to　be　effective　in　decreasing　SBP　and　DBP.　The　results　reconfirm　the　involvement　of　superoxide　anions　and　its　transportation　along　the　meridians,　and　demonstrate　that　EPD　between　acupoints　may　be　an　indicator　to　reflect　its　functioning　status.　Moreover,　preliminary　results　suggest　a　close　correlation　between　EPD　and　blood　pressure　readings,　implying　a　possibility　of　using　EPD　as　a　sensitive　parameter　for　blood　pressure　and　to　monitor　the　effect　of　antihypertensive　treatment.