Simultaneous measurements of ion composition and plasma drift velocity by the Bennett mass spectrometer on the Atmosphere Explorer-C satellite reveal a direct correlation between enhancements in NO+ concentration and ion drift velocity in the southern auroral oval. Low altitude (137 to 250km) data obtained between 1700 and 2400 hr magnetic local time on October 22, 1974 reveal a region of westward plasma flow at velocities up to 1.3 km/s between 62¿ and 68¿ invariant latitude, with corresponding NO+ enhancements of up to a factor of 20. A narrow region of reverse flow at ~0.9 km/s was also measured. These drift observations are consistent with convective flow patterns derived from electric field measurements, and their correlation with NO+ appears to support the suggestion that NO+ enhancements would be expected in regions of drift owing to the dependence on ion energy of the reaction O++N2→NO++N.