The effects of gamma irradiation on the stability of potassium clavulanate, amoxicillin sodium and their combination were investigated. A decrease in purity and increase in degradation products up to 30 days after the irradiation were evaluated by reversed phase HPLC. The comparison between unirradiated and irradiated amoxicillin sodium, performed within 24 h following the irradiation process, showed no significant increase in the pre-existing impurities and no evidence of newly induced degradation products. On the contrary, an appreciable increase in the content of some impurities was evidenced 30 days after the irradiation. The chromatographic profile of irradiated potassium clavulanate showed the appearance of one unidentified new product and a slight increase of one pre-existing impurity. No further change in the impurity content was noted 30 days after the irradiation. The amoxicillin sodium-potassium clavulanate combination underwent the same kind of radiation induced degradation as the single compounds.