Pancytopenia with severe thrombocytopenia occurred in a patient treated with low‐density lipoprotein (LDL)‐apheresis by polyacrylate adsorption from whole blood, after treatment frequency had been increased from once to twice a week. Cell counts recovered with discontinuation of LDL‐apheresis, but thrombocytopenia recurred after resumption of twice‐weekly treatments. Thrombocyte counts remained stable following the replacement of polyacrylate adsorption from whole blood by double‐filtration plasmapheresis. The complications' close coincidence with twice‐weekly polyacrylate adsorption from whole blood suggests a causal relationship, although by a still unknown mechanism. Monitoring of thrombocytes should be advised in patients treated with LDL‐apheresis by polyacrylate adsorption from whole blood. J. Clin. Apheresis 2010. © 2010 Wiley‐Liss, Inc.