Objectives To investigatesafety and effectivity of potassium inprevention ofrestenosis after PTCA. Methods Eighty patientswith PTCA were randomized into two groups: Controlgroup( Group Ⅱ n =40) with conventional therapy;Treatment group (Group Ⅰ n = 40) with conventionaltherapy plus oral potassium(Slow-K 1.2 g, q8h,given 3 days before PTCA and continued to the endofsub - study). Observation indeces of two groups werecompared in follow - up. Results Seventy - sevenpatients were followed -up(39 in group Ⅰ, 38 in groupⅡ) All blood indices (including fat, sugar, uric acid,cretonne, Na+, Cl-, Ca2+, Mg2+) except blood potas-sium in both groups were similar. Oral potassium couldincrease blood potassium level about 0.3 mmol/L ingroup I without causing any side effects. Suspiciousangina pectoris and evidence of myocardial ischemia byETT were developed in group Ⅱ had 14 patients(28.9% ) and Group I had 7 patients (17.9 % ); 6 of 17patients(35.3 % ) in group I and 11 of 21 patients ingroup II (52.3 % ) appeared restenosis confirmed bycoronary arteriography. 10.2 % in group I (4/39)and 23.7 % in group Ⅱ (9/38) needed revascular-izations (PTCA or CABG) Conclusions Therapywith potassium after PTCA showed that recurrence ofmyocardial ischemia, restenosis rate by follow-upcoronary arteriography and revascularization rate tendedto be lower in group Ⅰ than in group Ⅱ.