22 patients on chronic hemodialysis underwent low-molecular-weight-heparine (LMWH) (Fragmin, Kabi Chemie Corp., München) instead of conventional heparine (CH) for anticoagulation during dialysis. Blood evaluations before start, 2, 4 and 6 months under LWMH treatment and 3 and 6 months after switching back to CH were performed. During LWMH-treatment whole cholesterol decreased significantly, LDL-cholesterol being the main part accounting for this. HDL-cholesterol and the subfractions of HDL-cholesterol remained nearly unchanged. The apolipoproteins A1 and B decreased significantly, too. Apolipoprotein B decreased during the 6 months LMWH-period continuously, while Apolipoprotein A1 rapidly decreased during the first two months and then stabilized at a lower level. The triglycerides, starting from a normal range level, increased during the first 2 months significantly, then decreased reaching the starting values again at the end of the LMWH-period. Platelet aggregation induced with collagen showed a significant improvement during the use of LMWH. After switching back to CH the parameters returned to the starting values again.