In both African AIDS populations and homosexual populations outside of Africa, a high incidence of syphilis and multiple exposures to infectious diseases results in frequent, often abusive use of antibiotics. Epidemiological evidence exists for chemical immunosuppression resulting from antibiotics and other prescribed and recreational drugs prior to the current AIDS crisis. Analysis and review of literature is given on the effects of subcurative doses of antibiotics masking and distorting the expression of secondary and tertiary syphilis. A high incidence of seronegative syphilis is found in Africa and compares with Western reports of seronegativity and persistence of treponemes despite adequate antibiotic therapies. Late latent and tertiary syphilis produce symptoms and immunosuppression comparable to that seen in the current AIDS crisis. Screening procedures instituted for a group of gay men with AIDS and AIDS related conditions is revealing evidence of chemically immunosuppressed syphilis as a factor in AIDS.