Genotype tests establish which strain or strains of the Hepatitis C virus are present in your blood.  They are useful to the extent the genotype can be considered as an indicator of the prognosis and response to treatment. It is generally considered that genotype 2a responds better to Interferon treatment, while genotype 1b responds least.  However, this conclusion should not be taken as the definite truth, as researchers can reach different conclusions in the long term. For instance, in several cases that I know of first hand, in the combination treatment of Interferon plus Ribavirin long term remission was achieved not in relation to the genotype, but in direct proportion with the frequency interferon was administered (bi-daily regimen obtaining best results even in previous non-responders to the combination treatment). Therefore, genotype is probably not the best indicator of the possible outcome of treatment.  Long term remission was obtained irrespective of genotype. The only indicator of the treatment outcome was the viral load AFTER commencing treatment. Thus, patients whose viral load became undetectable within 2-4 weeks from the start of treatment got the best long term remission rate (the shorter the time, the better the response, irrespective of the viral load at the commencement of treatment).