Existing experimental and theoretical results are synthesized with new ion mass spectrometer data from Atmosphere Explorer C to provide a more comprehensive perspective on the understanding of nighttime equatorial irregularities. Particular attention is given to possible relationships between ionospheric holes and smaller-scale (3 m) irregularities observed by ground-based radar. Ion chemistry and transport considerations are found to support the concept that equatorial holes and equatorial spread F can be one and the same phenomenon, with the smaller-scale irregularities imbedded within the much larger scale ionospheric depletions.