1. 9 human volunteers, convalescent from infectious hepatitis experimentally induced by a strain of virus employed in this laboratory, were resistant when reinoculated with the same strain of virus, 6 to 9 months later.
2. 8 out of 12 previously healthy control subjects developed infectious hepatitis with jaundice following administration of this same material.
3. The demonstration of homologous immunity produced by this strain of virus is in agreement with the demonstration by others of homologous immunity produced by another strain of infectious hepatitis virus.