The organisation team reports the final program of the DDI 2011 – 2nd International Workshop on Regulatory Requirements and Current Scientific Aspects on the Preclinical and Clinical Investigation of Drug-Drug Interactions. The topics of the 2nd Marbach Castle meeting on regulatory and scientific aspects of drugdrug interactions (DDI), which will take place from May 1st to 3rd 2011, will be covered by renowned international scientists and experts from academia, pharmaceutical companies, contract research organizations, and consultancies. The program will provide a unique opportunity for scientific exchange and networking across company and organizational borders, and an opportunity to learn about the current state-of-the-art in the investigation of DDIs. The organizers are pleased to announce additional distinguished speakers from the USA (Michael Bolger, Uwe Christians, Andrew Parkinson, Alex Sparreboom, Karthik Venkatakrishnan) and Germany (Thomas Gramatte´, Wilhelm Haverkamp, Bernd Liedert, Christian de Mey).