In 1972, Magnius and Espmark on confronting different sera containing the surface antigen of hepatitis B with each other, demonstrated a new antigenic item which they called e. In later works the presence of this new antigenic specificity was associated with a greater rate of incidence of chronic hepatic lesion and a greater contagiousness of B virus. In the present study the e system was determined in a group of HBsAG positive blood donors and in a group of patients carrying HBeAG who had been admitted to the hospital for different reasons. The results showed an elevated rate of anti-e antibodies in the asymptomatic donors, and this could be correlated with clinical and biochemical indemnity of the liver function. HBsAg carriers mainly presented renal insufficiency or hematologic disorders, probably related to a deficient immune response. Determination of the e system shows its usefulness in enabling HBsAg positive carriers to be classified according to whether they present or not present hepatic lesion. The presence of HBeAg could be correlated with hepatic lesion, while HBeAc seems to determine some type of protection on those patients who have it in their sera.