The Tropical Rainfall Measuring Mission (TRMM) satellite was launched from Tanegashima space station in Japan on November 27, 1998, carrying a complement of instruments, including the Visible and Infrared Sensor (VIRS), the Lightning Imaging Sensor (LIS), the TRMM Microwave Imager (TMI), and the TRMM Precipitation Radar (PR). The PR provides high-resolution vertical reflectivity structure as well as attenuation measurements for surface rainfall estimation. The ground validation (GV) data consists of three-dimensional Cartesian reflectivity maps and statistics, 1.5 km rain rate maps, and stratiform/convective rain-type maps. Two recent TRMM overpasses of Melbourne, Florida (March 9, 1998) and Houston, Texas (June 6, 1998) of Mesoscale Convective Systems (MCS) has provided one of the first opportunities to make direct comparisons of the TRMM PR reflectivity values with those of the GV radars over equally sampled areas. Data from these overpass periods will be used to compare the measured reflectivity fields of both the PR and GV radars in order to estimate any relative calibration differences between the instruments. A comparison of the current TRMM stratiform-convective rain classification scheme (Steiner et al. 1995) to a modified version of the algorithm by (Listmaa and Biggerstaff 1998) will be also made. In this effort, the combined TRMM instrument measurements will be utilized in order to determine both the strengths and weaknesses of each approach