Results from an extensive survey of two Gulf of Mexico warm-core rings are presented. The data were taken during a 1-week period in December 1983 using a shipboard acoustic Doppler current profiler (ADCP), expendable current probes (XCP), expendable bathythermographs (XBT), and a CTD. Two rings were observed-an older one in the western Gulf adjacent to the west Texas shelf, and one just separated from the Loop Current. The western ring was of order 200 km in diameter with peak currents of 1 m s-1 at the 100-m level. Water properties were uniform and characteristic and the high-salinity Caribbean subtropical underwater. The eastern ring was of order 300 km in diameter with peak currents of near 2 m s-1 at the 100-m level. Water below 200 m is of Caribbean origin, while the surface waters show more variability suggesting some inflow of Gulf of Mexico common water. The evolution of the rings is also described based on the cruise measurements, satellite AVHRR, and other observations of opportunity. ¿ American Geophysical Union 1990