A coordinated rocket and ground-based study to investigate equatorial spread F irregularities is described. Measurements by the Jicamarca backscatter radar, ionosondes, and airglow instrumentation and of radio scintillations were correlated with high spatial resolution measurements of electron densities, particle fluxes, and VLF-ELF fields from a rocket probe. Experimentally, it is found that (1) very high positive and negative electron density gradients are responsible for the enhanced radar echoes, (2) energetic particles are not part of the spread F phenomena, (3) wave measurements are strongly correlated with the Doppler character of the radar signals, and (4) there is a one-to-one correspondence of the large-scale irregularities responsible for scintillations of satellite radio transmissions and ionosonde spread echoes with the small-scale irregularities responsible for the backscatter of VHF radar signals. The implications of the data are discussed.