Geosat altimeter observations covering most of the equatorial Atlantic between March and November 1987 were examined. Six ground tracks were selected with equator crossings between 15¿W and 23¿W longitude. At these locations there is evidence of westward propagating long waves during four repeat passes between July and October. Best fit parameters are phase velocity of 45¿6 cm s-1 and period of 25¿2 days. Waves are likely present over a wider range in longitude, but the observations are restricted by scan lines intersecting Africa to the east and noise associated with geoid undulations near the mid-Atlantic ridge to the west. A composite mean wave pattern was constructed between 8¿N and 8¿S latitude. The pattern resembles a somewhat distorted free mode. There are two off-equatorial maxima of 3.3¿1.0 near 4¿N and 2.6¿0.7 cm near 4¿S latitude. The northern maxima has a distinct NW-SE tilt of about 30¿. This is direct evidence of the transport of energy from the mean zonal flow into the wave. The kinetic energy replacement time is about 17 days. For comparison, an example of a shear instability wave in a simple rotating system is shown with the same sort of tilt as well as a free mode without a tilt.