RESUMEN
<p><b>OBJECTIVE</b>To investigate the microbial contents presented on the surface of mucosa in the oral cavity of patients who accepted radiotherapy, and to provide the evidences of controlling post-radiotherapeutic infections.</p><p><b>METHODS</b>32 patients (19 males and 13 females) aged from 37 - 72 received radiotherapy after oral squamous cell carcinomas operation were selected. Samples of saliva were obtained from the radiated center and opposite mucosa before and after radiotherapy. The detective amount, detective ratio and constituent ratio were analysed by cultivation and identification.</p><p><b>RESULTS</b>Streptococci, Candida albicans and Pseudomonas aeruginosa significantly increased on both sides of the oral mucosa while Neisseria and Actinobacillus decreased on radiated region after the radiotherapy.</p><p><b>CONCLUSION</b>Radiotherapy has great effects on oral bacteria and pathogenic organism may play a role in post-radiotherapy infections. It is necessary to do bacteria culture and choose sensitive antibiotics regularly for post-radiotherapeutic patients.</p>