The microbicidal effectiveness of pharmaceutical iodophor preparations comprising an organic substance which reacts with iodine to form a complex thereof, such as polyvinylpyrrolidone, iodine bound thereto in complex form, free iodine, and iodide ions, is assured by controlling the ratio of total iodine (complex bound iodine and free iodine) to iodide ions at between 2:1 and 10:1, this ratio being adjusted without chemical oxidizing agents such as iodate ions by anodic oxidation of a solution of the iodophor preparation and iodide ions. The resulting preparation can be free of chemical oxidizing ions such as iodate ions.
