The efficacy of the heparin-induced extracorporeal LDL-precipitation (HELP)-apheresis procedure has been studied in an open prospective multicentre trial. After 2 years of regular weekly HELP-treatment the data from 39 of 51 patients could be evaluated according to the study criteria. Twelve of the initially recruited study patients were omitted from the evaluation either because of premature termination of the treatment or because they did not fulfil the exact guidelines of the study protocol. A mean of 2.831 plasma was regularly treated on average every 7.85 days. The mean pre-/post-apheresis LDL-cholesterol levels decreased from 286/121 mg dl-1 at the first HELP treatment to 203/77 mg dl-1 after 1 year and to 205/77 mg dl-1 after 2 years of regular apheresis; the corresponding values for fibrinogen were 314/144, 246/98 and 250/105 mg dl-1, respectively. In contrast, the mean pre-/post-apheresis HDL-cholesterol levels rose from 41/38 through 51/44 mg dl-1 after 1 year to 52/43 mg dl-1 after 2 years of treatment. The overall result was a normalization of the atherogenic index (LDL-/HDL-cholesterol ratio) from 6.9/3.2 to 4.0/1.9. The angiographies from 33 patients obtained before and after 2 years of regular treatment could be evaluated blindly using the cardiovascular angiography analysis system. The mean degree of stenosis of all segments decreased from 32.5% (SD = 16) to 30.6% (SD = 16.8) over the 2 years. A regression > 8% was observed in 50/187 (26.7%) segments, whereas 29/187 (15.5%) segments showed progression. In 108/187 (57.8%) segments the lesions were stable (< 8% deviation) over 2 years. We conclude that regular treatment with HELP-LDL-apheresis is able to stabilize progressive atherosclerotic disease and to induce almost twice as much regression as progression of atherosclerotic lesions.