A sounding rocket launched to 927 km apogee during an auroral substorm encountered regions of large quasistatic electric fields (≤400 mV/m), ion conics (up to 700 eV maximum observed energy) and fluctuating electric fields near the oxygen cyclotron frequency. Since the fluctuating electric fields frequently exhibited spectral peaks just above the local oxygen cyclotron frequency and since the fluctuating electric fields were linearly polarized, we identify them as electrostatic oxygen cyclotron waves (EOCW). The maximum amplitude of the EOCW was about 5 mV/m RMS. The EOCW closely correlated with the presence of ion conics. Because of the relatively low amplitude of the EOCW and their relatively low coherence, we cannot conclude that they are solely responsible for the production of the ion conics. ¿ American Geophysical Union 1989