Whistlers recorded at Nainital (geomag. lat., 19°1Ń) on 25 March 1971 are used to measure the downward flux of ionization at low latitudes. The whistler data show a smooth decrease in dispersion with time from 00:20 to 05:20 h IST. This decrease in dispersion is interpreted in terms of a corresponding decrease in the electron content of tubes of ionization and is compared with that obtained by Park (1972, Technical Report, Stanford University) for mid-latitudes. The downward flux of ionization has been computed by means of an accurate curve fitting method developed by Tarcsai (1975, J. atmos. terr. Phys. 37, 1447) for reliable, routine analysis of whistlers with unknown nose frequency and causative sferic. The method is based on the least squares estimation of two parameters ( D 0 and ⨍ HE ) in Bernard's (1973, J. atmos. terr. Phys. 35, 871) approximation for the dispersion, and of a third parameter locating the causative sferic. The equatorial electron density and electron tube content N T values were computed using Park's (1972, Technical Report, Stanford University) expressions. Our whistler measurements demonstrate an average downward flux of 2.8 × 10 8 electrons cm −2 s −1 between 00:20 and 05:20 IST on 25 March 1971. The ionization flux is computed again from the simple diffusion equation which relates the flux to the ionization gradient through the ambipolar diffusion coefficient. It is shown that the flux thus computed is within an order of magnitude less than that derived from the dispersion data. It is, therefore, argued that other processes like E × B drifts should play a dominant role in controlling the transport of ionization at low latitudes.