Particle contamination of blood always takes place in extracorporeal systems and few studies have been conducted to evaluate potential risks. Particle concentration was measured in the efferent blood line on original equipment for two established LDL elimination procedures (DALI) (Fresenius) and Liposorber (Kaneka). Acquired data were compared with standards for infusion solutions from European (EP) and American (USP) Pharmacopoeia. All values were well below the given limits. Even in extreme situations (>20 pump stops) particle concentration did not exceed the standards. Considering an average treated blood volume of 7.31 for the DALI-System and 17.01 for Liposorber (long term clinical studies) the absolute amount of particles infused per treatment was 167,000 (DALI) and 465,000 (Liposorber) particles > or = 2 microm.