Abstract: The present invention is related, but is not restricted, to the field of the study or analysis of materials by determining the chemical or physical properties thereof, in particular the field of the investigation or analysis of materials by using electromagnetic waves, specifically providing a method from measuring internal stress in tires, using a ferromagnetic material. The invention provides a method for measuring internal stress in a tire, characterized in that it comprises: incorporating into the tire a material that is a combination of a rubber matrix and a plurality of microwires made of a ferromagnetic material; irradiating said tire with electromagnetic waves by means of a transmitting antenna; receiving an electromagnetic wave absorption response from said tire by means of a receiving antenna; and determining the internal stress of the tire by means of a processor operatively connected to said receiving antenna, on the basis of the electromagnetic wave absorption response.