Methods of preventing or reducing mucositis in patients who have been exposedto toxic levels of radiation or who are undergoing treatment with platinum-containing anti-tumor compounds are provided. The methods compriseadministering an effective amount of a protective agent comprising methionineor a methionine-like moiety to said patient prior to, simultaneously with, orsubsequently to exposure to radiation or administration of a platinum-containing anti-tumor compound. Combinations of these time periods can also beemployed.
