Aims. In dialysis patients, blood transfusions and long-term dialysis are well known risk factors for transmission of hepatitis C virus. In this study the impact of use of dedicated hemodialysis (HD) units on the anti-HCV conversion rates was studied in patients of two different hemodialysis units in a city, Kayseri, between October 1995, and March 1999. Materials and methods. In the HD Unit of Erciyes University (HUEU), anti-HCV-positive and -negative patients were dialyzed on the dedicated machines in the same big room and seropositive patients for HBsAg in isolated rooms. In the HD Unit of Kayseri State Government Hospital (HUSH) only seronegative for anti-HCV and hepatitis B patients were treated. If a patient became positive, the patient was transferred to HUEU. Seventy-five patients have been receiving hemodialysis therapy in HUEU. Thirteen HBsAg-positive and 62 HBsAg-negative patients were dialyzed in separate rooms. Of 62 HBsAg-negative patients, 22 (35.5%) were already positive for HCV antibody when they started dialysis or before the study period. Forty seronegative patients (64.5%) for anti-HCV (23 males, 17 females) were treated with 22 anti-HCV-positive patients in the same room in HUEU. The mean duration of dialysis treatment was 24.7 +/- 21.0 months (range 4 to 96 months). Of the 40 patients, 28 (70%) became positive during the study period. Of 28 patients who became seropositive, 10 (35.7%) had a history of blood transfusion. Fifty-four patients (21 males, 33 females) were treated in HUSH during the study period. The mean duration of dialysis treatment was 19.3 +/-9.6 months (range 5 - 41). Eight patients (14.8%) became anti-HCV-positive. Of these, 7 had received blood transfusion (88%). Results. The seroconversion rate of patients in HUEU was higher than that of HUSH (odds ratio 3) (p < 0.05). Data derived from our patients showed that contamination appeared to be both transfusional and nosocomial and that there is a possibility of transmitting HCV infection in hemodialyzed patients never submitted to blood or blood products transfusion. Nosocomial spread of HCV in HD units which both seropositive and seronegative patients treated together was higher than that of dedicated unit. This is true even though we separated anti-HCV-positive dialysis machine.