The Fifth International Symposium on the Characterisation of Porous Solids (COPS-V) was held at Heidelberg, Germany, from May 30 to June 2, 1999. About 220 participants from 25 countries enjoyed a very successful meeting with 32 lectures and 155 poster presentations.The Symposium started with a highly stimulating lecture by Sir John Meurig Thomas, Cambridge, highlighting the recent developments in engineering of new catalysts. The following two full sessions were devoted to theory, modelling and simulation which provide the basis for the interpretation of pore structural data of adsorbents and finely dispersed solids. Sessions 2 and 3 focused on the advances in the synthesis and characterisation of highly ordered inorganic adsorbents and carbons. Sessions 4 and 5 addressed important questions with respect to the characterisation of porous solids by sorption measurement and other related techniques.The intensive three-day programme provided a stimulating forum for the exchange of novel research findings, concepts, techniques and materials which are collected in this volume.