Using electron spin resonance (ESR) free radicals, present naturally or formed after γ- irradiation of parts of coffee bean, were examined by entrapping the sample in potassium chloride powder in ESR quartz tubes. The ESR signal at g = 2.002 was more prominent in the spermoderm than in the whole seed portion of the coffee beans. The γ-irradiation of coffee beans with doses of 5 or 10 kGy, normally used for decontamination, resulted in a dose-dependent increase of a signal at g = 2.002 which was accompanied by a weak triplet (aH c. 3.0 mT), and which was also more prominent in the spermoderm. While short-term storage (24 h at 2 5 ± 0. 5 °C) of irradiated beans resulted in a substantial loss of signal at g = 2.002, annealing at 50 ± 0.5 °C for 16 h increased this signal intensity in greater proportion than caused by irradiation alone, suggesting that generation of free radicals in the two varieties of coffee beans is not unique to the irradiation processing alone.