A case of acute sepsis caused by Gaffkya tetragena in an adult with acquired hypogammaglobulinemia has been described. The Authors pointout the importance that particular conditions of disreactivity and/or of immunodeficiency can play in the acquistion of pathogenicity by Gaffkya tetragena. In the case under discussion a high deficit of IgG and IgA was demonstrable, which had previously caused a long series of infective bacterial diseases.