Investigation of the relationship between the percentage occurrence of equatorial plasma bubbles/range spread F irregularities (EPBRSI) and the Quasi-Biennial Oscillation (QBO) of the lower-stratospheric mean zonal wind in the equatorial zone reveals a QBO-modulation effect has also been found: the percentage occurrence of EPBRSI increases (decreases) in the easterly phase of the QBO in the Indian-East African sector (in the American sector) and decreases (increases) in the westerly phase of the QBO in the Indian-East African sector (in the American sector). It is suggested that this represents new evidence that the low-latitude ionosphere is modulated by atmospheric planetary waves from below. ¿ American Geophysical Union 1993