ThisvolumeofLNCScontainstheproceedingsofthe6thEuropeanPerformance EngineeringWorkshop, held at ImperialCollegeLondon during July 9-10,2009. Thiswasthe?rstintheEPEWseriestobeheldintheUK, followingonfromthe highly successful workshops that were held in Toledo (2004), Versailles (2005), Budapest (2006), Berlin (2007) and Palma de Mallorca (2008). As with previousEPEW workshops, the event was supported by submissions from all over the world, including Asia, the Middle East, North America, as well as Europe. There were 33 submissions in total of which 13 were selected for full papers and four as short papers. I would like to commend the diligent e?orts of the Programme Committee, who returned a complete set of reviews - four per paper - which is most unusual. This enabled and enhanced the week-long programme discussion which selected the papers presented here. The papers themselves maintained the tradition of diversity and quality that the European Performance Engineering Workshop has supported throughout. Papers representing the di?erent ?elds of performance engineering and ana- sis, were broadly classi?ed by applications, techniques and formalisms. In the applications domain, we had a signi?cant contribution, I believe for the ?rst time, in the modelling of auctions and markets. There were also contributions on hardware modelling of RAID systems, as well as ?ve papers on performance aspects of cellular and ?xed-line networks. New techniques presented included a novel approach to mean value analysis, an application of stochastic ordering to queueingnetworksandaninterestingextensionofpassage-timeanalys