Abstract: Different methods for preparing methionine methyl sulfonium iodide were compared. Methyl iodide was found to be a more satisfactory methylating agent than methyl sulfate or methanol-sulfuric acid. When methyl iodide was used with water as medium, the yield of the sulfonium salt was improved to 92 per cent from 75 per cent as reported by Atkinson et al. Methionine methyl sulfonium chloride was prepared from the iodide by anion exchange with freshly prepared silver chloride in 96.6 per cent yield.