The aim of present study was to assess the radioprotective effects of the local application of amifostine to treat acute buccal mucositis in guinea pigs. A total of 32 guinea pigs were randomized into four groups: (Group A) topically administered 50 mg of amifostine plus radiotherapy (RT); (Group B) 100 mg amifostine plus RT; (Group C) normal saline plus RT; and (Group D) normal saline plus sham RT. The opportunity for administration was 15 min before irradiation. When administered, the cotton pieces that had been soaked with 0.5 ml amifostine solution or saline were applied gently on the buccal mucosa of each guinea pig for 30 min. The animals in Groups A, B and C were irradiated individually with a single dose of 30 Gy to the bilateral buccal mucosa. Eight days after irradiation, the animals were scored macroscopically; they were then euthanized, and the buccal mucosal tissues were processed for hematoxylin-eosin staining and ICAM-1 immunohistochemical analysis. In Groups A and B, the mean macroscopic scores were 2.9 ± 0.6 and 2.4 ± 1.1, respectively. There was no significant difference between the two groups (P > 0.05). However, when they were separately compared with Group C (4.4 ± 0.7), a noticeable difference was obtained (P < 0.05). No mucositis was observed in Group D. Comparisons of the expression of ICAM-1 were in agreement with the macroscopic data. Histologically, superficial erosion, exudate and ulcer formation were all observed in the RT groups; only the severity and extent were different. The microscopic observations in the amifostine-treated groups were better than in Group C. The results demonstrated that topical administration of amifostine to the oral mucosa is effective treatment of acute radiation-induced mucositis.