A capillary electrophoresis/mass spectrometry (CE/MS) for the simultaneous analysis of methamphetamine (MA) and related compounds has been developed. The compounds are MA, amphetamine, dimethylamphetamine, ephedrine, norephedrine, methylephedrine, 3,4-methylenedioxymethamphetamine, 3,4-methylenedioxyamphetamine, and 3,4-methylenedioxy-N-ethylamphetamine. The CE/MS system used in this study is a CE with a quadrupole MS detector. Several volatile acids and salts were examined as electrolytes, and 100 mM ammonium acetate (pH 7.0) gave the best CE separation and MS sensitivity. The detection limit of MA was 0.03 μg/ml using the SIM mode. The compounds, which were not separated by CE, could be identified by a CE with an ion trap MS/MS detector using MS/MS measurement.