The objective of this multicenter trial, which included 28 clinical centers, was to determine if repeated low density lipoprotein (LDL)-apheresis using the Liposorber LA-15 system (Kaneka Corporation, Osaka, Japan) could lead to an additional acute and time averaged lowering of total cholesterol (TC) and LDL-cholesterol (LDL-C) in severely hypercholesterolemic patients whose cholesterol levels could not be controlled by appropriate diet and maximal drug therapy. A total of 6,798 treatments were performed on 120 patients, including eight homozygous familial hypercholesterolemia (FH), 75 heterozygous FH, and 37 unclassified FH or other hyperlipidemias, from 1988 through 1994. The mean TC and mean LDL-C levels at baseline were 410.0 and 333.9 mg/dl, respectively. LDL-apheresis was performed once a week or at least once every 2 weeks in all patients. During treatment with the Liposorber system, the mean acute percentage reduction was 52.6% for TC and 63.1% for LDL-C. Very low density lipoprotein cholesterol (VLDL-C) and triglycerides (TG) were also substantially reduced to 60.6% and 47.5%, respectively. Fibrinogen, a potential risk factor for coronary heart disease (CHD), was reduced by 26.2%. In contrast, the mean acute reduction of high density lipoprotein (HDL) was only 3.4%. The adverse events (AE) were those generally associated with extracorporeal treatments. The most common AE was hypotension, with 69 episodes corresponding to 1% of all treatments reported in 44 of the 120 patients treated. All other kinds of AE occurred in <0.2% of the treatments. The treatment with the Liposorber LA-15 system was overall well tolerated. It should be noted, however, that a more severe type of hypotensive reaction was reported in patients taking concomitant angiotensin converting enzyme (ACE) inhibitor medication. With the exception of such anaphylactoid-like reactions associated with the intake of ACE-inhibitors, the Liposorber LA-15 system represents a safe and effective therapeutic option for patients suffering from severe hypercholesterolemia that could not be adequately controlled by diet and maximal drug therapy.