329 patients were evaluated from 1978 to 1990. 40 new cases of non-A non-B hepatitis were observed, all regarding patients on hemodialysis. Since the beginning of 1989, we introduced measures to limit the diffusion of the virus: reduction to a minimum of blood transfusions and a new disinfection protocol for monitors, instruments and surroundings. Of the 40 new cases, 30 took place between January 1985 and March 1989, only 2 later. If we consider the annual incidence before and after the introduction of preventive measures, we can observe a significant reduction in NANB hepatitis incidence in the last 2 years.