During the last week of September 1968, ESRIN (the European Space Research Institute) held the ESRIN-ESLAB Symposium on 'Low-Frequency Waves and Irregularities in the Ionosphere' in Frascati, near Rome. The symposium was attended by about 60 participants, including speakers from most of the ESRO member states, the U.S.A., the U.S.S.R., and Peru. The main topics covered were: (a) observations of ionospheric irregularities by radar scattering, (b) scintillations of satellite signals, (c) geomagnetic micropulsations, and (d) whistlers. Both theoretical and observational aspects were treated. In...