Abstract Objective. Low saliva flow and abnormal saliva composition are common conditions after radiotherapy for oral cavity and pharyngeal cancer. Both conditions increase the susceptibility to dental caries and erosion, which may be further accelerated by changes in food preferences. The aim of this study was to determine changes in saliva flow and susceptibility to erosive challenges in pharyngeal cancer patients before and after radiotherapy to the head and neck. Materials and methods: The erosive potential of sucking acidic candies with and without calcium was determined in nine patients (50-68 years) before and after receiving a radiation dose of 66 Gy to the head and neck area. The erosive potential was evaluated from saliva degree of saturation with respect to hydroxyapatite (HAp) and by dissolution of HAp in candy-stimulated saliva. Results. Sucking acidic candies increased saliva flow rates ∼ 17-fold before as well as after radiotherapy (p <0.001). However, significantly lower unstimulated (p <0.05) and stimulated (p <0.01) saliva flow rates were obtained after radiotherapy. Also, saliva became more under-saturated with respect to HAp during (p <0.01) and in a period after sucking the candies (p <0.01). HAp dissolution was significantly lower with the candy containing calcium compared with the control candy, both before and after radiotherapy (p <0.001 and p <0.05). Conclusions. Radiotherapy to the head and neck area significantly reduced saliva flow and altered saliva composition in a way that may increase the susceptibility to dental disease. However, saliva could be stimulated by acidic candies, which could be made nearly non-erosive even in irradiated patients.