OBJECTIVE The long-term effects of the replacement of conventional heparin by low-molecular weight heparin (LMWH) on lipid parameters were examined in a large group of hemodialysis patients. METHODS One-year prospective investigation. METHODS Renal units. METHODS A total of 93 patients aged 12-63 years old receiving hemodialysis for 51 (1-172) months were studied. None of the patients had primary hyperlipidemia, diabetes mellitus, or other secondary causes of dyslipidemia. METHODS In all patients administration of LMWH was introduced in doses 2500-5000 units. METHODS Baseline values of lipoprotein profile prior to the intervention were compared with results obtained after 3, 6 and 12 months of LMWH. RESULTS During of LMWH treatment a small but statistically significant decrease of total and HDL cholesterol (from 200 +/- 45 mg/dl to 185 +/- 42 mg/dl, p < 0.01, and from 45 +/- 11 mg/dl to 42 +/- 10 mg/dl, p < 0.05, respectively), as well as Apo B (from 128 +/- 36 mg/dl to 121 +/- 35 mg/dl, p < 0.001) was noticed. Moreover, triglycerides decreased significantly (from 175 +/- 73 mg/dl to 146 +/- 62 mg/dl, p < 0.001). The beneficial effects of LMWH were more pronounced in patients with dyslipidemia (total cholesterol > 200 mg/dl, or triglycerides > 200 mg/dl) before the replacement of conventional heparin. CONCLUSIONS The long-term use of LMWH instead of conventional heparin for anticoagulation during dialysis has beneficial effects on the lipoprotein profile, especially in patients with dyslipidemia.