The Italian crystallographic community gladly announces that the XL National Congress of the Italian Crystallographic Association (AIC) will be held in Siena on September 19- 22, 2011 and invites all scientists from crystallographic and related disciplines to participate to this event.The Scientific Committee and the Local Organization have assembled a scientific program of the highest quality, that covers a wide range of topics such as crystal growth, methods and techniques for structure determination, molecular recognition, polymer and material science, molecular medicine and structural biology. The aim is to offer the latest developments and topics in the field of structural sciences in a interdisciplinary framework.Outstanding scientists from Italy and abroad, including the 2009 Nobel Prize for Chemistry, Prof. Venkatraman Ramakrishnan, have accepted to give plenary talks and keynote lectures.The congress is inserted in the scenario of the city of Siena which will offer to the participants the occasion to merge science with art in the unique atmosphere of a beautiful medieval city. SCIENTIFIC SESSIONSMS1 Comprehensive approach to structural characterizationMS2 Molecular recognition and self assemblyMS3 Structure determination for medicinal chemistryMS4 Crystal growth and defectsMS5 Highlights of Italian crystallographyMS6 BiocrystallographyMS7 Crystalline porous materials PLENARY LECTURESVenkatraman Ramakrishnan – CambridgeAlain Baronnet – CRMCN-CNRS MarseilleKari Rissanen – Jyväskylä University