Cancer and chemotherapy are amongst leading health problems influencing the quality of life of the individual. The complications of many treatment regimens appear frequently in the mouth, and cause serious problems. Although mucositis has been a subject of interest to scientists for more than 20 years, this has not resulted in development of standard procedures for prevention and management. The aim of this study was to examine the effect of oral cryotherapy on the development of mucositis in patients receiving Chemotherapy. This quasi experimental study was conducted at the respiratory disease clinic, at the National Cancer Institute in Cairo on 60 patients with bronchogenic carcinoma under chemotherapy; 30 randomly allocated to study group with oral cryotherapy, and 30 allocated to the control group. Data collection tools included demographic data sheet, patient-judged mucositis grading, physician-judged mucositis grading, and oral pH measurement. Data were collected before the first chemotherapy course, and for 21 days. Physician-judged mucositis was done on days 2, 3, and 21. Oral pH measurements were done on days 1, 2, 3, and 21 using Merck Universal Indicator. Cryotherapy was done using special ice cubes with rounded corners. Patient-judged mucositis grading was highest on day 6 in the study (40.0%) and control (80.0%) groups, The differences between the study and control groups in the changes in pH values after chemotherapy were statistically significant at the four days of assessment, p < 0.001. It is concluded that oral cryotherapy shifts the pH of saliva to alkaline, and thus can prevent mucositis development and it's severity in patients undergoing chemotherapy. Therefore, it is recommended that oral cryotherapy be initiated five minutes before infusion and maintained during infusion of chemotherapeutic agents that can cause mucositis, with further research to study the effect of oral cryotherapy in subsequent courses of chemotherapy