A method for estimating tropical cyclone intensity and size from Advanced Microwave Sounder Unit (AMSU) observations has been developed using Atlantic and east Pacific tropical cyclone cases collected during the 1999 and 2000 hurricane seasons. A statistical retrieval algorithm is used to determine temperature profiles and vertically integrated cloud liquid water from the AMSU-A radiance measurements. A correction for attenuation by cloud liquid water and ice scattering is applied to the retrieved temperature profiles. Hydrostatic and gradient wind constraints are used to calculate the pressure and tangential wind of the tropical cyclone as a function of radius and height. Because of the limited spatial resolution of the AMSU-A data (48 km at nadir), the inner cores of strong tropical cyclones are not fully resolved, so that the retrieved gradient winds underestimate the observed maximum winds. To correct for this problem, parameters from the AMSU temperature, cloud liquid water, pressure and wind retrievals are statistically related to the observed storm intensity (maximum surface winds) and size (radii of 34, 50 and 64 kt winds). A validation of the intensity and size estimates for an independent sample of Atlantic and east Pacific storms from the 2001 hurricane season will be described. A brief description of the intensity and size algorithm will also be presented.