The aim of this study is to determine the effect of laser therapy employed to prevent oral mucositis resulting from chemoradiation. This study is a random single blind one. The patients with healthy oral mucosa receiving radiotherapy and chemotherapy for their oral cavity and salivary glands with any reason for the first time with the age range of 12-70 will participate in this study. The patients with the history of chemoradiation, pregnancy, diabetes and light sensitivity are excluded from the study. A total of 46 patients will be divided into 2 groups of 23 individuals. The selection procedure will be as follows. The patients referring will be assigned a number drawn from a box where numbers 1to 50 is already put in it. A number is taken from the box for the first patient and if the number is odd, the patient will be assigned to the experimental group and if the number is even, he/she will be assigned to the control group. The next person with the same age and gender will be assigned to the opposite group. That is, if the first person is a 63 year old female and has the odd number, the second 60 year old female will be sent to the control group. If the next patient does not match the first one, he/she will be randomly assigned according to odd/even number. Both groups of chemoradiation regimen will have cisplatin in a dose of 30 mg/m2 every week (intravenous infusion), and 4-5 hours before or after that, radiotherapy with daily administration of 180- 200 cgray, 5 days a week will be carried out. All the patients will rest for 2 days (conventional method). All selected patients will be receiving radiotherapy for their oral cavity and salivary glands. They will receive chemotherapy in combination with radiation at the same day for 5 successive days with wave length of 630 nanometers, power of 30 mw and dose of 5 j/cm2. The radiation will target 10 spots about 8mm in diameter in oral cavity. In the laser off group, laser therapy with off device will be followed. The patients in both groups will be examined by the researcher every other day for 30 days, and the required information will be gathered in data collection forms. At the end of the treatment, the degree of oral mucositis, xerostomia and the patients’ satisfaction will be analyzed.