A radio method for the measurement of winds in the ionosphere is described. A pulse transmitter working on about 4 Mc/s is used in conjunction with three receivers placed at the corners of a right-angled triangle, and separated by distances of the order of 100 m. A simultaneous record is made of the fading of a single radio pulse reflected from the ionosphere and received at the three receivers. If a steady wind is blowing in a non-turbulent ionosphere the three fading records are displaced in time and the velocity and direction of the wind can be deduced. Many of the records obtained are sufficiently simple for reliable deductions to be made.The results of 82 determinations of winds by the use of local pulse transmitters are presented in Figs. 7, 8 and 9 in the form of histograms. The most frequent velocity is found to be of the order of 50 m/sec in a direction towards north-west, but there are clear indications that this velocity varies throughout the day, probably with a semi-diurnal period. The results are compared with previous measurements made by other methods.Measurements have also been made in which a distant pulsed transmitter has been used in conjunction with the same arrangement of receiving aerials. In all the experiments care was taken to avoid the misleading conclusions which may be drawn when “polarization fading” occurs owing to the simultaneous presence of two magnetoionic components in the reflected pulse.