An improved procedure for the methylation analysis of oligosaccharides and polysaccharides is described. Steps in the procedure were examined and optimised for quantitative recovery and speed. Methylation was shown to be complete by using [14C]methyl iodide. All operations were performed in the same tube and the need to concentrate solutions containing acetylated alditols of methylated sugars was eliminated, thus minimising losses due to volatilization. The method is convenient, gives high recoveries of acetylated alditols of methylated sugars, and allows analysis of the glycosyl linkages of oligo- or poly-saccharides to be completed within a working day. A wide range of oligo- and poly-saccharides were methylated by this procedure.