INTRODUCTION: Clinical implication of HCV quasispecies is not well-known. Available methods for their detection are time consuming and expensive. ----- AIMS & METHODS: Aim of this study was detection of HCV quasispecies. Serums from 109 subjects were first genotyped by standard INNO-LIPA HCV II method. After that, same samples were analyzed by high-resolution DNA melting analysis as follows: ribonucleic acid was isolated with commercial kits and afterwards transcript by polymerase chain reaction. Amplification of hypervariable region 1 (HVR1) was done in two phases. Obtained mix for each sample was cycled in Light-cycler and fluorescence was detected. Collected Tm's for each sample was showed as melting curve with 4 variables: Tm, high (H), wide (W) and area (A). Each variable was statisticaly correlate with non achieved treatment response. ETVR means undetectable HCV RNA at the end of treatment and SVR means maintenance of undetectability of HCV RNA at 6 months after the completion of treatment. Non achieved treatment response means still detectable HCV RNA at those treatment points. Second sample was collected in 40 untreated pts, and in 24 treated pts (45/69 achieved ETVR). ----- RESULTS: total of 109 subjects, 18 to 71 years old, 64 men, more with 1 (59.6%), majority with medium fibrosis according to Ishak score (53.8%). Obtained results were: mean Tm 86.8±2.10; mean H 1.64±0.74; mean W 3.38±0.14 and median A 4.42. Correlation of no achieved ETVR and SVR was positive with Tm, H and A and negative with W. Statistical significance was found for A as positive predictor of SVR: OR=1.44, 95%CI (OR) =1.03-2.03, p 0.033. Statistical significance was not found between pared samples in any of parameters but difference in mean has been noticed: Tm2, W2 and H2 increased but A2 decreased in untreated group. In treated group: Tm2 increased while H2 and A2 decreased. Statistical significance was noticed for W2 (Wilcoxon Signed Ranks -1,871; p = 0,061). ----- CONCLUSION: Determination of HCV quasispecies in single sample can predict the treatment response. Changes of quasispecies in untreated and treated group of patients have been observed.