{Note: This treatment is for theoretical uses. Validations of effectiveness and safety for various uses are needed. Negative effects HAVE been experienced by some people ingesting chlorine dioxide or injecting intravenously} "pharmaceutical composition for systemic, particularly parenteral treatment of infectious diseases, based on an aqueous, sterile and pyrogen-free solution of chlorine dioxide, which contains 5 to 1000 mg/l (ppm) dissolved chlorine dioxide (CI02) and preferably 3 to 10 g/l of an ionic tonicity regulator, optionally in combination with a non-ionic tonicity regulator. The composition additionally preferably contains a pH regulator, particularly a pH buffer system, adjusted to pH 7.3-7.5, and can furthermore contain DMSO or MSM. In the ready-to-use state, the composition is free of chlorate ions, hydrochloric acid and gaseous chlorine, or contains said components in a concentration of 1 mg/L (1 ppm) at maximum each.