Abstract: Objective: To observe the effect of malignant melanoma treated with fast neutron. Methods: Twenty one cases of malignant melanoma treated during December 1991 to January 1998 were reviewed. Results: 11 cases survived more than one year, 7 cases more than three years, and 2 cases more than five years. Conclusion: Fast neutron therapy is one of the effective methods in the treatment of malignant melanoma.