Hepatitis C is an infectious disease caused by Hepatitis C virus (HCV) and characterized by development of inflammation as well as fibrosis. On the other hand, the extracellular nucleotides and adenine nucleosides are important signaling molecules that can modulate inflammatory responses in platelets and lymphocytes. This study sought to determine the activities of ectoenzymes [ectonucleoside triphosphate diphosphohydrolase (E-NTPDase), ecto-5 -nucleotidase (E-5 -NT) and ecto-adenosine deaminase (E-ADA)] that metabolize nucleotides in platelets and lymphocytes and to evaluate cytokine levels of patients with HCV. Twenty five HCV patients and fifty healthy subjects (control group) were selected for this study. In lymphocytes, was observed a lower ATP hydrolysis (P<0.001), and higher ADP hydrolysis (P<0.001) and E- ADA activity (P<0.001) in HCV patients when compared to the control group. In addition, the results revealed a higher ATP and ADP hydrolysis by E-NTPDase and higher E-ADA activity in platelets of HCV patients when compared with the control group. Also, IL-4 and IL-10 were significantly (P<0.05) increased while IL-6 was decreased (P<0.05) in HCV patients. In conclusion, the results showed that the activities of E-NTPDase and E-ADA were altered in both lymphocytes and platelets of HCV patients. These alterations in enzymes activities may be possible regulatory mechanisms in an attempt to manage liver damage and ongoing inflammatory process. Furthermore, decreased IL-6 as well as increased IL-4 and IL-10 in HCV patients may suggest an antiinflammatory process and possible compensatory mechanisms in minimizing liver injury. / Hepatitis C is an infectious disease caused by Hepatitis C virus (HCV) and characterized by development of inflammation as well as fibrosis. On the other hand, the extracellular nucleotides and adenine nucleosides are important signaling molecules that can modulate inflammatory responses in platelets and lymphocytes. This study sought to determine the activities of ectoenzymes [ectonucleoside triphosphate diphosphohydrolase (E-NTPDase), ecto-5 -nucleotidase (E-5 -NT) and ecto-adenosine deaminase (E-ADA)] that metabolize nucleotides in platelets and lymphocytes and to evaluate cytokine levels of patients with HCV. Twenty five HCV patients and fifty healthy subjects (control group) were selected for this study. In lymphocytes, was observed a lower ATP hydrolysis (P<0.001), and higher ADP hydrolysis (P<0.001) and E- ADA activity (P<0.001) in HCV patients when compared to the control group. In addition, the results revealed a higher ATP and ADP hydrolysis by E-NTPDase and higher E-ADA activity in platelets of HCV patients when compared with the control group. Also, IL-4 and IL-10 were significantly (P<0.05) increased while IL-6 was decreased (P<0.05) in HCV patients. In conclusion, the results showed that the activities of E-NTPDase and E-ADA were altered in both lymphocytes and platelets of HCV patients. These alterations in enzymes activities may be possible regulatory mechanisms in an attempt to manage liver damage and ongoing inflammatory process. Furthermore, decreased IL-6 as well as increased IL-4 and IL-10 in HCV patients may suggest an antiinflammatory process and possible compensatory mechanisms in minimizing liver injury.