A comprehensive ground validation program, known as LBA-TRMM, will be carried out in Amazonia from 1 November 1998 to 28 February 1999. This program will focus on studying the dynamical, microphysical, electrical and diabatic heating characteristics of tropical convection in this region. Data collected in the field campaign will be used in part to validate products from the TRMM. Indeed, the characteristics of convection in this climate-sensitive region are poorly understood, especially properties such as the organization and vertical structure of convective clouds, precipitation mechanisms and the diurnal cycle of rainfall. The research to be done will center on the planned deployment of two radars, the NCAR S-pol 10 cm polarimetric radar, and the TOGA C-band Doppler radar. These radars will be used in a dual-Doppler configuration to provide 3-D wind fields, as well as improved rainfall estimates (from S-pol). Atmospheric sounding systems, two aircraft, a lightning network, raingauges, disdrometers and a profiler will also be deployed. The aircraft will include the NASA ER-2 which will observe microwave brightness temperatures, X-band radar cloud structure and ambient electric fields, and the UND Citation which will provide in-situ sampling of cloud microphysical and thermodynamic properties. These data will also serve as an important validation source for multiparameter radar-based hydrometeor identification algorithms. Coincident sampling of tropical rainfall with S- and C-band radars will aid in the improvement of reflectivity- based attenuation algorithms at C-band. LBA-TRMM will be conducted in parallel with the wet season component of the Large Scale Biosphere-Atmosphere Experiment in Amazonia. The field project will be centered near Ji-Parana in the state of Rondonia (in west central Brazil). We will report on data collection activities and preliminary findings at the conference.