Observations from four GPS RO missions: Global Positioning System/Meteorology (GPS/MET, Ware et al., 1996), CHAallenging Minisatellite Payload (CHAMP, Wickert et al., 2001), Satellite de Aplicaciones Cientificas-C (SAC-C, Colomb et al., 2003) , and Constellation Observing System for Meteorology, Ionosphere and Climate and Taiwan's FORMOsa SATellite Mission #3 (COSMIC/FORMOSAT-3, Rocken et al., 2000) are collected which are located within a 850 km radius and 1.5h time window of all observed tropical cyclones (TCs) from 1995 to 2006 that was recorded in the hurricane best-track reanalysis data set (Jarvinen, et al., 1984). A composite analysis of tropical cyclone structure is carried out using these data. Preliminary results show that the radial structure of temperature and moisture fields from GPS ROs compares favorably with those obtained previously using ground based radiosonde measurements (Frank, 1977) and aircraft reconnaissance data (Gray and Shea, 1973; Shea and Gray, 1973; LaSeur and Hawkins, 1963; Jorgensen, 1984a,b). Intensity and geographical dependences of TC structures revealed by GPS RO data are also examined. Differences between global analysis and GPS RO observations within TCs are quantified. It is concluded that GPS RO observations will contribute significantly to the understanding and modeling of TC structures, especially those related to vertical variability of the atmospheric state within TCs.