Objective: To investigate oral Candida strain diversity in patients receiving radiation therapy for head and neck cancer compared to controls by conventional procedures, including cultivation of imprint samples on chromogenic medium and subsequent identification using Analytical Profile Index testing. Method and Materials: Twenty-two irradiated patients aged 18 to 55 years were recruited from the Maxillofacial Prosthetic Service, Mahidol University. Concomitantly, 22 healthy individuals whose age and sex matched that of the patient group were selected for a control group. Results: All patients studied were Candida carriers and were predominantly infected with Candida albicans (86.36%). Besides C albicans, other yeasts colonizing the oral cavity of these patients were C glabrata, C krusei, and C tropicalis. Candida carriage was found relatively less frequently (45.45%) in control subjects. However, C albicans was still the predominant species detected. No C dubliniensis was found in either group. Conclusion: Head and neck cancer patients who had received radiotherapy had a high prevalence of Candida colonization in the oral cavity. Consequently, prophylaxis to reduce Candida infection in these patients is required. This may improve the quality of life for patients who receive irradiation treatment for malignant cancer. Keywords: Candida, oral colonization, radiotherapy