Seventy five Saudi children, 55 with sickle cell anaemia and 20 with beta thalassaemia major, who were negative for all hepatitis B virus (HBV) markers five years ago were recently investigated for exposure to HBV and hepatitis C virus (HCV) infection. Of the 55 patients with sickle cell anaemia and 20 with beta thalassaemia major, 20 and five patients respectively had been vaccinated against HBV earlier and all of them still had protective antibody (anti-HBs 42-96 IU) 3-5 years after vaccination and there was no vaccine failure. Among the non-vaccinated children the exposure rates to HBV were 14.3% among those with sickle cell anaemia and 26.7% among those with beta thalassaemia and this was not statistically significant when compared with the exposure rate to HBV among the general paediatric population (20.1%). Anti-HCV positivity among those with beta thalassaemia major and sickle cell anaemia was 70% and 18.2%, respectively, and this was significantly higher than anti-HCV positivity among the control group (0.8%). Anti-HCV positivity was directly related to the amount of blood transfused and to the duration of transfusion. The results of the study show that although the exposure rates to HBV among patients with sickle cell anaemia and beta thalassaemia major were not significantly different than that among the general paediatric population, infection with HBV still takes place among non-vaccinated patients despite strict precautionary measures taken. Hence early vaccination against HBV would probably be the only effective way of controlling HBV infection. For HCV infection, and because a vaccine against HCV is still not available, preventive measures such as blood screening for anti-HCV before transfusion and stringent infection control measures are crucial steps to be implemented for the control of spread of HCV among these groups of patients.