Globally, over 4% of the world population is affected by hepatitis C virus (HCV) infection. The current standard of care for hepatitis C infection is combination therapy with pegylated interferon and ribavirin for 48 weeks, which yield a sustained virological response in only a little over half of the patients with genotype 1 HCV. We investigated the clinical importance of pharmacogenetics in treatment efficacy and prediction of hematotoxicity. A total of 148 patients infected with HCV were enrolled. All patients were treated for a period of 48 weeks or less with pegylated interferon and ribavirin. Four genotypes were investigated: inosine triphosphatase (ITPA) rs1127354, C20orf194 rs6051702, interferon lambda (IFNL)3 rs8099917, IFNL3÷4 rs12979860 in the population from southwestern Romania. Genetic variants for rs129798660 and rs6051702 proved once more to represent an indisputable clinical tool for predicting sustained virological response (SVR) (69.23%, chi-square p=0.007846, p<0.05 and 63.29%, chi-square p=0.007846, p<0.05, respectively). ITPA genetic variants protect against ribavirin-induced hemolytic anemia and C20orf194 also proved to be protective against thrombocytopenia. These clinical findings strengthen the belief that pharmacogenetics should play a constant role in treatment decisions for patients infected with hepatitis C virus.