Following the decrease in HAV endemic levels in the last decades, nowadays in Italy most people aged less than 30 years are susceptible to the infection. We have tested for serum anti HAV IgG 194 chronic hepatitis patients from Naples to evaluate the level of protection against HAV in a category of patients in whom an acute necrosis due to HAV might induce liver failure. The study shows that 90.7% of Neapolitan chronic hepatitis patients has serologic evidence of prior HAV infection. Specifically, 98.1% of the patients over 40 years of age, but only 54.6% of those under 40 tested positive for anti HAV IgG. 102 patients had cirrhosis and only one tested negative. The data suggest that HAV vaccination in susceptible chronic hepatitis patients should be judged by the physicians in care on the basis of the severity of disease, patient's age, real risk of exposure to the infection, and level of education.