Serological and virological tests are useful in management of HCV patients, and include anti-HCV antibody assays, measurement of HCV RNA and HCV genotyping. They are used to diagnose infection, initiate treatment and assess the virological response to antiviral therapy. Monitoring of viral kinetics during the early phases of antiviral treatment is crucial in making treatment decisions concerning arrest of treatment and optimization of its duration. A 2-log drop in viral load at week 12 (early virological response) has good negative predictive value when assessing the sustained virological response (SVR), as most patients without a 2-log drop in viral load at week 12 will not attain a SVR. In contrast, undetectable HCV RNA at week 4 (rapid virological response) has good positive predictive value, as patients with undetectable HCV RNA at week 4 have high probability of reaching a SVR. Recent data suggest that some rapid responders can be treated for shorter periods than usually recommended without compromising their chance of a sustained response. On the other hand, slow virological responders infected with genotype 1 should be treated longer to increase the probability of viral eradication. Future studies should focus on identification of the earliest criterion which is both highly sensitive and highly specific in order to predict early SVR and nonresponse, as well as to avoid useless treatment prolongation.