Background/Aims: The role of postoperative radiotherapy (PORT) in head and neck mucosal melanomas (HNMM) is not yet clearly defined. The aim of this study is to report the 21-year experience of the Brazilian National Cancer Institute in such treatment. Methods: From January 1983 to December 2003, 31 patients with confirmed histological diagnosis of HNMM underwent treatment at the Brazilian National Cancer Institute. Of these, 20 received radical treatment with surgery alone (8 patients – group 1) or surgery and PORT (12 patients – group 2). Results: Local control and the median time to local failure at 5 years were 75% and 14 months for group 1 and 83.5% and 40 months for group 2 (p = 0.06). The overall survival rates at 3 years were 37.5% for group 1 and 58% for group 2. At 5 years the survival rates were 25% for both groups (p = NS). When PORT was initiated within 60 days after surgery, there was a trend towards improvement in overall survival (p = 0.08). After univariate analysis, distant metastasis, location of primary disease and tobacco smoking were important prognostic factors. Conclusion: Early (<60 days) PORT for HNMM provides better local control with a longer disease-free survival.