Dialysis patients are among groups at risk for development of hepatitis C infection (HCV). The aim of the study was to evaluate the prevalence and the incidence of seroconversion for HCV in five haemodialysis units in Morocco. The study was conducted during the period from September 2003 to September 2004. We studied 303 patients (148 females), mean age 49+/-16 years; dialysis duration was higher than five years in 64% of the cases. The prevalence of HCV infection was evaluated by using a fourth generation enzyme immunoassays. In the seronegative patients, we performed anti-HCV tests at three and six months intervals and monthly testing of alanine aminotransferase (ALT) activity and assessment of anti-HCV tests if the ALT activity was elevated. Moreover, risk factors, such as blood transfusion, surgery and other invasive procedures were recorded. Seroprevalence of HCV was 68.3%. Among 85 patients who were tested negative for anti-HCV at the entry of the study, four (4.60%) seroconverted in six month (estimated incidence: 9.41 new cases per year). HCV seropositivity was associated with longer duration of dialysis (p=0.000), and previous blood transfusions (p=0.047). The follow-up of the ALT in the seronegative patients did not show any significant variation. In conclusion, the prevalence and incidence of HCV infection in haemodialysis units in Morocco are dramatically elevated. High incidence seropositivity suggested nosocomial transmission of HCV; the dialysis processes itself, and blood transfusions are important risk factors for HCV transmission in these patients.