Hepatitis C virus (HCV) envelope glycoprotein-2 (E2) inhibits the interferon (IFN)-induced, double-stranded RNA activated protein kinase (PKR) via PKR eukaryotic initiation factor-2α phosphorylation homology domain (PePHD). Present study examined the genetic variability of the PePHD in patients receiving interferon therapy. The PePHD region from HCV genotype 1a/1b infected patients receiving IFN was amplified by reverse transcriptase polymerase chain reaction (RT-PCR) and analyzed using bidirectionaly sequencing. The PePHD sequence was different in pretreatment isolates from three months treated patients. It was shown that the major PePHD quasispecies could change after three months IFN therapy and in one patient; the major PePHD quasispecies could change after six months IFN therapy. These mutations were occurred at codons 665, 666 and 667 of followed-up samples and at codons 660, 661, 666 and 670 of randomly treated patients. Some of these mutations were similar to those reported in previous studies. Other mutations were also detected in upstream and downstream regions of PePHD which may have influenced the structure, conformation and configuration of this region and thereby suppressing PePHD inhibitory properties. In conclusion our data suggested that HCV E2 PePHD may play an important role in determining the interferon response among Iranian HCV infected patients.