Background Anticardiolipin antibody (aCL Ab) is considered one of the contributory factors in the development of acute ischemic stroke. Chronic hepatitis C virus infection (HCV) and the antiphospholipid syndrome are two conditions that have increased the risk of stroke. The aim of this study is investigate the prevalence of anticardiolipin autoantibodies IgM (ACA IgM), in serum samples of patients with chronic HCV infection and their relationship to the severity of the viral infection. The study was performed on 75 Egyptian subjects, 25 healthy volunteers and 50 patients of both sexes; all patients were HCV-4a. And divided into two groups according to their real time (RT) PCR into, 25 patients with low viremia, (HCV-RNA) less than 106 lU/ml and 25 patients with high viremia (HCV-RNA) more than 106 lU/ml. All subjects after fasting for twelve hours and stored for the determination of aminotransferases (ALT, AST) and γ-GT enzymes activities, and anticardiolipin autoantibodies IgM. There is very highly significant increase of serum ACA (IgM) MPL (U/ml) in patients with high viremia and low viremia when compared to the control group (p <0.0001 for both) and high significant increase in patients with high viremia when compared with low viremia (p <0.0001). Also there is high significant correlation between serum ACA (IgM) and quantity of HCV-RNA in both high and low viremia patients. But no significant correlation between serum ACA (IgM) serum ACA (IgM) and serum liver enzymes.