Abstract: The effects of many usual penetration enhancers such as azone(AZ) ,oleic acid(OA),poloxamer 188(POL 188)and propylene glycol(PG)on the blood glucose level in diabeticrats after transdermal iontophoresis of insulin were studied.The change of blood glucose level(D%),defined as the percent ratio of the concentration of blood glucose in rats after the iontophoreticapplication of insulin to that before administration of insulin, was used to present the data. The resultsshowed that following iontophoretic application of insulin for 3 h, the D%in diabetic rats treated with100%AZ and 5%AZ/PG was 38.58%and 25.28%respectively, and the D%in diabetic ratsuntreated with enhancers was 45.48%.The D%in diabetic rats treated with 100%OA,10%OA/PG,10%POL 188/PG and 10O%PG was 66.28%, 60.47%, 76.75%and 57.93%respectively.So,AZ showed a synergistic effect on the ability of iontophoresis to promote skinpermeation of insulin, and PG further increased this effect.The combination of AZ, PG andiontophoresis increased the permeation of insulin significantly.OA,POL 188 and PG did not displaysynergistic effect on iontophoresis enhancement.The combination of iontophoresis and some enhancersprovided a novel idea and possibility for the administration of polypeptide drugs.