The common side effects of head and neck radiotherapy and/or chemotherapy are oral mucositis, hyposalivation/xerostomia, and severe pain. This chapter describes how low level laser therapy (LLLT) can be used as an auxiliary therapy for salivary gland stimulation, improving patient quality of life. It is important to differentiate between xerostomia, which is the subjective feeling of dry mouth, and hyposalivation, which is the objective evidence of reduced saliva flow rate. Several treatments have been described to minimize the severity of oral side effects induced by radiotherapy and/or chemotherapy. One concern about laser application is whether the biostimulation of salivary glands promoted by irradiation results in an increase in saliva secretion or only the relief of symptoms of xerostomia. Some clinical studies of salivary gland irradiation have demonstrated that LLLT is effective in increasing saliva flow rate, reducing mouth dryness, and biomodulating tissue inflammatory processes.