Radar observations of the equatorial electrojet at oblique incidence made by the Cornell University Portable Radar Interferometer (CUPRI) from Alca⁁ntara, Brazil show the same east-west asymmetry in the echo strength seen previously at Jicamarca, Peru, namely type-I echoes from the west are stronger than those from the east [Balsley, 1965>. One early theory attributed the results at Jicamarca to topographical asymmetries with the Andes Mountains to the east and the Pacific Ocean to the west [Ierkic et al., 1980>. However, the lack of comparable topographical features at Alca⁁ntara now implies that this postulate is no longer tenable. Other proposed theories are then examined, but none has so far been found to be fully consistent with both the CUPRI and the Jicamarca data.¿ 1997 American Geophysical Union