The first three cases of spotted fever group rickettsiosis from Thailand are reported. The patients presented with fever, headache, lymphadenopathy, and petechial maculopapular rash. One patient also had an eschar and overt evidence of confusion. An indirect fluorescent antibody test, an indirect immunoperoxidase test, and an enzyme-linked immunosorbent assay demonstrated a broad, strong reactions of the sera of the patients with spotted fever group rickettsia antigens of many species, but not with antigens of typhus or scrub typhus rickettsiae. All three patients responded to treatment with a single dose of doxycycline.