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Background/Aim:Hepatitis C virus genotypes 4 (HCV-4) is the most prevalent genotype in Saudi Arabia, although it's various subtypes, mode and route of transmission remains unknown. The aim of this study was to analyze (i) the variability of the HCV-4 subtypes, the route and source of HCV transmission and (ii) the influence of HCV-4 subtypes on their therapeutic response.Patients and Methods:Sixty-four HCV-4 patients were analyzed retrospectively for the prevalence of various sub-genotypes and the possible mode of transmission, and it was correlated with their treatment response to pegylated interferon (PEG-IFN) α-2a and ribavirin therapy.Results:Positive history of blood or blood products transfusion was noted in 22 patients (34%), hemodialysis in 10 patients (15.6%), surgery in 7 patients (11%), and unknown etiology in 25 patients (39%). Prevalence of HCV-4 subtypes was 4a = 48.4% (31/64), 4d = 39% (25/64), 4n = 6.25% (4/64), and remaining combined (4m, 4l, 4r, 4o) 6.25% (4/64). No significant correlation between subtypes and the source of transmission was recognized (P = 0.62). Sustained virological response in all HCV-4 patients was 64% (41/64), while in each subtypes separately it was 4a 77.4% (24/31), 4d 52% (13/25), and combined (4n, 4m, 4l, 4r, 4o) 62.5% (5/8) (P = 0.046).Conclusion:No obvious cause for the mode of HCV transmission was noted in majority of the patients. No significant correlation was observed between HCV-4 subtypes and the source of HCV infection. 4a and 4d subtypes were the most common in Saudi Arabia, and patients infected with 4a subtype responded significantly better to combination therapy than to 4d subtype.