Hepatitis C virus (HCV) is an enveloped single stranded RNA virus belonging to the genusrnHepacivirus within the family Flaviviridiae. It causes an acute or chronic necroinflamatoryrndisease of liver. Due to shared risk factors of transmission, co-infection with HIV is common.rnThe aim of this study was to assess the impact of HCV co-infection on immunohaematologicalrnand clinical chemistry parameters in HIV patients before and after HAART. 387 HIV infectedrnpatients at Yekatit-12 and Zenbaba General Hospitals were screened for HCV infection and 25rnof them were found HCV/HIV co-infected. From those 25 co-infected patients, 9 of them werernpre-ART and the rest 16 were under HAART patients. All those 25 HCV/HIV co-infected patientsrnwere observed for 4 years for their annual and quarterly changes in immunohaematological andrnclinical chemistry parameters. For this study, leftover blood samples collected forrnimmunohaematological and clinical chemistry tests were used. Flavicheck-HCV two-siternsandwich, 4th generation EIA was used for the detection of total antibodies specific to HCV inrnserum or plasma. CD4+ and CD8+ T-cells were counted using FACS counter (BectonrnDickinson), haematological tests were done using Celldyn-1800 haemoanalyzer and liverrnenzymes were measured using Humastar80 chemistry analyzer. From the result, HCV/HIV coinfectionrnprevalence was 6.5% (7.3% for males and 5.5% for females) and from the 25 coinfected,rnmore males were co-infected than females (60% Vs 40%). The percentage increments inrnCD4+ and CD8+ T-cells of co-infected patients were lower than HIV mono-infected patientsrn(131% Vs 432%) and (14% Vs 31%) respectively. It is highly associated with increased liverrnenzymes in both pre-ART and under HAART co-infected patients. In conclusion, if confirmed inrnlarge studies, it is advisable for HIV patients to screen HCV before initiation of HAART in orderrnto minimize HAART associated liver damage and for better management of HIV in HIV/HCV coinfectedrnindividuals.rnKey words/phrases: Immunohaematological, Pre-ART, HCV/HIV co-infection, HAART, CD4+,rnCD8+, GOT, GPT, ALP