Abstract In this paper, noon values of f 0 E s at Kodaikanal are studied to find lunar tidal variations in the equatorial sporadic- E-layer ( E sq type). It is shown that the phases of lunar diurnal and semidiurnal variations in f 0 E s and f b E s are in agreement with those of the H-component of the Earth's magnetic field, the agreement with f b E s being more clear. The amplitude of lunar variation in f 0 E s at Kodaikanal is smaller than that found at Ibadan and Huancayo. The variation in f ⊙ E s is predominantly semidiurnal in high sunspot period, while the diurnal component, though almost equal in high as well as low solar activity, dominates over the semidiurnal one in low sunspot period. The phase of lunar semidiurnal variation of f 0 E s practically remains same in both the sunspot epochs, but that of the diurnal variation changes by 4–9 hr. The close agreement between the lunar variations of f b E s (and f 0 E s ) and horizontal component of the Earth's magnetic field at the equator suggests that the strengthening or weakening of E s ionization is controlled by the same physical process as is responsible for the increase or decrease in the Earth's magnetic field at the equator.