Satellite measurements of sea-surface temperature (SST) by the TRMM Microwave Imager reveal previously unreported features of tropical instability waves (TIWs). In the Pacific, TIW-related variability is observed from the eastern boundary to at least 160 ¿E. Cusp-shaped distortions of SST fronts and associated trains of anticyclonic vortices both north and south of the equator propagate westward at ~0.5 m s-1 with approximately 50% larger meridional displacements in the north. In the Atlantic, TIWs and associated anticyclonic vortices are clearly observed only on the north side of the equator where they propagate from the eastern boundary to the western boundary at ~0.3 m s-1. ¿ 2000 American Geophysical Union