The aim of this study was to evaluate the efficacy of two chemotherapeutic agents against bacterial forms responsible for prosthesis-related infections.The evaluation was made on the basis of a count using optical microscope 1000x after GRAM staining of the main bacterial forms found in periprosthetic inflammatory exudate both before and after treatment. Two drugs used: ornidazole and minocycline. A group of 20 patients were studied (12 women and 8 men) aged between 42 and 71 years old with an advanced stage of periprosthetic inflammatory pathology. The pharmacological protocol was administered to the two groups of patients for a period of approximately 15 days.At the end of treatment there was a marked reduction in all the bacterial forms involved in periprosthetic pathology in both groups, with a gradual recovery of normal bacterial flora (gram forms) coupled with a clinical improvement in the implant sites examined.Given the specificity of action shown by ornidazole against pathogenic anaerobic, gram-; bacteroides and sporigenic forms, it is recommended for systemic use against prosthesis-related inflammatory disease.