Analytical method for saccharin in foods was developed using gas chromatography/mass spectrometry(GC/MS). Methylation with diazomethane, acetylation with MBTFA, and silylation with MSTFA and MTBSTFA were compared. Methylation of saccharin produced N-methylated saccharin as the major product and O-methylated saccharin as the minor one. Silylation of saccharin with MSTFA and MTBSTFA reasulted in the formation of the correponding O-silylated products, respectively. The derivatization of saccharin was optimized with MSTFA. The ions at m/z 240, 255, and 166 were monitored to characterize saccharin.