A total of more than 350 mesoscale convective systems (MCSs) were identified and studied for the warm seasons of 1996-1998. These systems were initially broken into four infrared satellite classifications according to their size, shape, and duration: mesoscale convective complexes (MCCs), persistent elongated convective systems (PECSs), meso-ß MCCs (MßMCCs), and meso-ß PECSs (MßPECSs). Using 2-km national composite reflectivity data, the growth stage of each MCS was analyzed resulting in a classification of MCS development by the different types of interaction between convective cells and convective clusters. In addition, soundings were obtained from the standard National Weather Service (NWS) upper-air network to provide some information about the environment in which these systems formed. The classifications and environmental data provided information to explore the differences between various classes of MCSs and the differences in MCS development.