Electron spin resonance (ESR) is used to date archaeological materials by studying the daily increase of the ESR absorption signal intensity. Conventional ESR dating has so far been applied to geological minerals, fossil shells, corals, and bones and is based on the accumulated radiation damage created by natural radiation. However, a new ESR dating method is presented which utilizes the chemical reaction for peroxide radical formation in organic materials; this is applicable in forensic science, archaeology, and authenticity testing. Measurements were made of paper, furs, cotton, silk and wool textiles and other archaeological materials like Japanese lacquer Urushi, using a commercial spectrometer with 100 KHz field modulation. Papers of distinctly different ages of about six months, ten years, and about 200 years were tested. Besides dating, ESR was found to be useful for other purposes. As the bonding of the aforesaid materials is attacked by oxygen-the effect of which is peroxide radical formation (this is the object of ESR measurement) and hence the deterioration of those materials-the decomposition of archaeological materials can be prevented if they are stored in a cool and inert atmosphere. During the experiments, the peroxide radical formation was markedly reduced in a vacuum or in an inert atmosphere at 15-20°C. -- AATA