To investigate the efficacy of reducing plasma lipoprotein(a) (Lp(a)) as well as low density lipoprotein cholesterol (LDL-C) levels on the prevention of restenosis after PTCA, LDL-apheresis was attempted on a total of 54 patients at six institutions. LDL-apheresis using a dextran sulfate cellulose column has been proven to be an effective method for reducing both plasma Lp(a) and LDL-C levels. As a subgroup (apheresis-drug combined group), 29 of the 54 patients were given Pravastatin (HMG CoA reductase inhibitor) and Niceritrol (Nicotinic Acid) in addition to LDL-apheresis to maintain low plasma levels of both Lp(a) and LDL-C through the follow-up period of 5 months after PTCA. Patients whose plasma Lp(a) levels were reduced by more than 50% showed a lower restenosis rate than those whose plasma Lp(a) levels were reduced by less than 50% (21.2% vs. 52.4%, P = 0.0179), especially in patients with high plasma Lp(a) levels above 30 mg/dl where a much lower restenosis rate (15.0%) was observed. Furthermore, in the apheresis-drug combined group, the restenosis rate was 11.8% regardless of baseline plasma Lp(a) levels, including even those below 30 mg/dl. In conclusion, in patients with high plasma Lp(a) levels, a greater than 50% reduction in Lp(a) levels by LDL-apheresis is effective in preventing restenosis after PTCA. If the plasma Lp(a) reduction rate is greater than 50%, LDL-apheresis combined with lipid-lowering drugs such as niceritrol and pravastatin seems to be more effective, even in patients with low plasma Lp(a) levels.