The tumoricidal and antiviral effects of Staphylococcal toxins are well documented. In a preliminary study we investigated the immune modulating properties of these toxins by administering single oral doses of a 12c potency of a lysate of Staphylococcus aureus Cowan I, to 4 healthy probands and 12 HIV infected patients with clinical symptoms. We observed a decrease of circulating immune complexes in the healthy probands as well as in the HIV positive patients, accompanied in the latter by a significant increase of CD4 lymphocytes, CD4/CD8-ratio and an improvement of the HIV related symptoms. None of the dose dependent toxic effects commonly found in Staphylococcal sepsis were noticed. Further research on the immune modulating effects of potencies of bacterial superantigens is suggested, especially in view of a possible treatment for HIV infected and other immune compromised patients.