Post-radiation caries, a rapidly progressing and highly destructive type of dental caries, is one of the most common post- radiation complications in patients with head and neck cancer. Topical fluoride application has been shown in clinical studies to reduce post-radiation caries in irradiated patients. This study reviewed 148 patients who had received radiation for head and neck cancer. All the subjects received pre-radiation dental care. After radiation, the first group consisted of 53 patients who were under regular 3 months dental recall and received topical fluoride applications. The second group consisted of 95 patients who did not return for regular dental recall. Result from clinical examination and bitewing radiographs revealed that the caries indexes were 7% and 31% for the first and second groups, respectively. Chi-Square test showed significant difference between the two groups (P value less than 0.005). Regular topical fluoride application is valuable in reducing dental caries after radiation for head and neck cancer.