Hepatitis C virus (HCV) is a major public health problem and is considered the most common etiology of chronic liver disease in Egypt. Antiviral therapy for HCV infection has improved significantly in recent years and typically includes 24 to 48 weeks of therapy with pegylated interferon α (PEG-IFN α) and ribavirin; now it is 12-24 with newer therapies. Results from different laboratories, indicate that successful immunity against HCV involves potent T helper 1 (Th1) cellular responses. Several studies indicate that certain probiotic bacteria possess the ability to promote Th1-cell responses. These cells produce IFN-γ, which has direct antiviral effects. Aim of work: Find out the effect of probiotic bacteria on the cellular immune response of HCV infected patients before and during treatment with pegylated interferon alpha and ribavirin (standard therapy) through testing the effect on IFN-γ production. Patients and methods: The study was conducted on 60 HCV RNA positive patients who were fit for SOC therapy consisting of Peg-Interferon and Ribavirin. Patients were randomly subcategorized into two main groups, Group 1 (probiotic group) which received the SOC therapy plus probiotic bacteria – Lactobacillus rhamnosus GG (LGG) ( 30 patients) and Group 2 (placebo group) which received the SOC therapy plus placebo (30 patients). Results: It was found that the levels of IFN-γ in sera of the placebo and probiotic group patients showed SVR ranging from 36.36 – 50.02 pg/ml (mean ± SD = 43.19±6.83) and 39.26 - 51.94 pg/ml (mean ± SD = 45.6 ±6.3) respectively . So, there was no statistically significant difference in the IFN-γ level between placebo and probiotic groups (p value = 0.268). On comparing response to treatment in both groups, in placebo group: 17 (70.8%) patients achieved SVR and 7 (29.2%) patients were non responders, while in probiotic group, 18 (72%) patients achieved SVR and 7 (28%) patients were non responders. So, there was no statistically significant difference between both groups in response to treatment (p value= 0.928). Conclusion: Combination of probiotics with SOC therapy for treatment of chronically infected HCV patients did not improve the response to treatment significantly.