Observations of partial reflections from the ionosphere at vertical incidence at 2.66 MHz have been made at Resolute Bay, geographic latitude 74.7 °N, since September 1963. By measuring the amplitudes of the ordinary and extraordinary backscattered waves information is obtained about electron number densities in the lower ionosphere. The results presented in this paper show that the partial reflection technique is more sensitive than most other ground-based experiments for the detection of D-region ionization increases associated with small solar proton events. Results obtained by the partial reflection experiment during the events of 5 February 1965 and 16 July 1966 are presented and compared with VLF and satellite observations.