Sera from healthy donors and four groups of subjects with acute viral hepatitis were tested for anti-HAV IgM by ELISA with hepatitis A virus antigen grown in tissue culture. The results were compared with those obtained by formalin inactivated HAV from 'HAVAB-M' test kit (Abbott Laboratories, USA). With both preparations of antigens, sera from healthy donors and patients suffering from acute hepatitis B or non-A, non-B did not show anti-HAV IgM antibodies whereas acute phase sera from hepatitis A patients showed strong reactions indicating the presence of anti-HAV IgM antibodies. The results indicate similarity in the specificity of both preparations of HAV against anti-HAV antibodies and encourage the use of tissue culture derived HAV for serological diagnosis of hepatitis A.