Radio pulses have been used as a probe to investigate scattering characteristics of ionospheric irregularities in the D - region at a frequency of 1.98 MHz, at Adelaide, South Australia (35¿S). The angular distribution of the returned energy was investigated as a function of time and height. Distinct layers of strong scatter have frequently been detected, the heights of which differ on different days. The layers appear to be of two distinct types - those occurring above 80 km and those below - the two groups having different temporal and angular characteristics. The higher layers exhibit scatter from a much larger range of off-vertical angles, and the power returned from them varies less in time than for the lower layers, which tend to show short 'bursts' of scatter.