The Aerodyne Aerosol Mass Spectrometer (AMS) provides size-resolved chemical composition of non-refractory (vaporized at 600°C under vacuum) submicron aerosols with a time resolution of the order of minutes. Ambient measurements were performed in Tokyo between February 2003 and February 2004. We present intercomparisons of the AMS with a Particle-Into-Liquid Sampler combined with an Ion Chromatography analyzer (PILS-IC) and a Sunset Laboratory semi-continuous thermal-optical carbon analyzer. The temperature of the AMS inlet manifold was maintained at > 10C above the ambient dew point to dry particles in the sample air (relative humidity (RH) in the inlet < 53%). Assuming a particle collection efficiency of 0.5 for the AMS, the mass concentrations of inorganic species (nitrate, sulfate, chloride, and ammonium) measured by the AMS agree with those measured by the PILS-IC to within 26%. The mass concentrations of organic compounds measured by the AMS correlate well with organic carbon (OC) mass measured by the Sunset Laboratory carbon analyzer (r = 0.67–0.83). Assuming the same collection efficiency of 0.5 for the AMS organics, the linear regression slope is found to be 1.8 in summer and 1.6 in fall. These values are consistent with expected ratios of organic matter (OM) to OC in urban air.