A virus hepatitis B was observed intercurrently in 8 patients with malignant lymphomas or plasmacytoma respectively. Four of these patients where the therapy of the basic disease was discontinued after manifestations of hepatitis came to death by acute liver dystrophy. The therapy was continued in the remaining four patients without any changes, hepatitis showed a tendency towards an involution with remaining HBsAg carrier status. In our opinion these four cases clearly indicate that, naturally by carefully observing the situation of the liver, a continuation of the envisaged treatment might involve a smaller risk than limiting the treatment.