The majority of this volume is devoted to Chapter 1 which is entitled 'Verification and New Development of International Reference Ionosphere' covering the presentations both by invited and submitted papers. Together with the earlier volume, Advances in Global/Regional Descriptions of Ionospheric Parameters, it reports on the foremost research by the working group IRI during the 1990-92 period. The papers which relate to particular problems complement specific publications where the basis and algorithms used to establish the computer code (at present IRI 90) are described. On the basis of the code, the monthly averages for the electron density, ionic and electron temperatures and ionic composition of the still and non-aurorale ionosphere can be established. Since the creation of the IRI, the constant improvement of the description, based on carefully selected observation has led to increasingly elaborate presentations. This entailed th