Non-A, Non-B hepatitis and their sequelae seem to be as frequent as HBV infections in Morocco. These diseases represent an important problem of public health because their high incidence and high fatal rate. Some aspects of the epidemiology of Non-A, Non B acute hepatitis were evoking a high incidence of enterically transmitted hepatitis E. That was confirmed by serum studies having shown that hepatitis E antibodies were detected in more than 60% of patients with acute Non-A, Non-B hepatitis. However this type of hepatitis has been recognized only as sporadic (non-epidemic), mainly transmitted by personal contacts in low hygiene conditions. Other Non-A, Non-B acute hepatitis (around 35%) were certainly due to hepatitis C virus infection, because the presence of hepatitis C antibodies in the serum of the patients. However, in our study, hepatitis C seemed to be rarely transmitted by transfusion or other blood related route. Chronic liver diseases related to Non-A, Non-B virus infection appeared to be as frequent as the ones due to hepatitis B virus. Serological studies had shown that about seventy-four per cent of the studied cases were related to an infection by hepatitis C virus (presence of hepatitis C antibodies). Among other Non-A, Non-B chronic liver diseases the possible existence of some cases due to hepatitis E virus infection cannot be ruled out but this hypothesis needs further investigations to be verified. The prevalence of the markers of past hepatitis B infection in convalescent patients from Non-A, Non-B hepatitis is comparable to the prevalence of hepatitis B infection markers in blood donors. However, chronic HBV infection could be a factor facilitating the clinical expression of the Non-A, Non-B hepatitis.