The mechanism of the antithrombotic action of statins is unclear. We evaluated the effects of atorvastatin on the coagulation parameters and homocysteine levels of patients with primary hypercholesterolemia. Forty-four patients with primary hypercholesterolemia were treated with atorvastatin 10 mg/d for 24 weeks at Adnan Menderes University Medical Faculty, Division of Hematology, Aydin, Turkey. We evaluated the effects of atorvastatin on homocysteine; lipid parameters such as total cholesterol, low-density-lipoprotein (LDL) cholesterol, very-low-density-lipoprotein (VLDL) cholesterol, triglycerides, high-density-lipoprotein (HDL) cholesterol, lipoprotein (a), apolipoprotein Al and apolipoprotein B; and coagulation parameters such as fibrinogen, antithrombin-III, protein C, protein S, von Willebrand factor, D-dimer, partial thromboplastin time and prothrombin time; and hematological parameters such as hemoglobin, white blood cell and platelet counts, vitamin B12 and folic acid. Atorvastatin significantly decreased the levels of total cholesterol, LDL cholesterol (p< 0.001), VLDL cholesterol, triglycerides and apo B (p< 0.001). The level of HDL cholesterol significantly increased with atorvastatin treatment (p< 0.001). Atorvastatin significantly increased the levels of fibrinogen (p< 0.001), but it had no effect on other coagulation factors and homocysteine (p> 0.05). After treatment, while vitamin B12 levels significantly increased (p< 0.05), other hematological parameters were not changed with atorvastatin (p> 0.05). Although there were beneficial effects of atorvastatin on lipid parameters, atorvastatin did not significantly change the level of homocysteine and hematological, and coagulation parameters, with the exception of fibrinogen and vitamin B12 levels.