Background: Stent restenosis has been known to be related with allergic reaction to the metalic components of the stent. Therefore, we sought to evaluate and compare the allergic reaction after the insertion of conventional Arthos stent and new carbon coated Arthos Inert stent. Methods: From the April 2002 to June 2004, 128 patients (male: 100, mean age 60짹10 years old) were enrolled in the study. The patients were randomly assigned to Arthos or Arthos Inert stent and were scheduled to be followed at 6 months. Clinical diagnosis included 64 acute myocardial infarction, 20 unstable angina and 44 stable angina. All patients were encouraged to do skin patch test for 4 components of stent (potassium dichromate, nickel sulfate, manganese chloride and molybdenum) at 6 months. Allergic reaction was interpreted by 2 different dermatologists at 48 and 72 hours after the patch attachment. Results: Risk factors included hypertension in 79(62%), hypercholesterolemia in 66(52%), diabetes mellitus in 28(22%) and smoking in 17 patients(13%). Risk factors, culprit lesion, angiographic lesion severity and angiographic parameters (reference diameter, lesion severity and lesion length) was not different between 2 groups. Positive allergic response after patch test included 30%, 23%, 36% and 2% to potassium, nickel, manganese and molybdenum each. Positive response after skin patch test included 39%(5/13) in Arthos group and 58%(18/31) in Arthos Inert group (p=0.161). Also, stent restenosis occurred in 29%(13/45) in Arthods group and 20%(10/49) in Arthos Inert group. Conclusion: Restenosis rate after new carbon coated stent tended to be lower, but was not different statistically. Also, allergic reaction was not different between 2 groups.