The present volume is based on papers presented at the 6th Workshop on M- brane Computing, WMC6, which took place in Vienna, Austria, in the period July 18-21, 2005. The ?rst three workshops were organized in Curtea de Arge, s, Romania - they took place in August 2000 (with the proceedings published in Lecture Notes in Computer Science, volume 2235), in August 2001 (with a sel- tion of papers published as a special issue of Fundamenta Informaticae, volume 49, numbers 1-3, 2002), and in August 2002 (with the proceedings published in Lecture Notes in Computer Science, volume 2597). The fourth and the ?fth workshopswereorganizedinTarragona, Spain, in July2003, andin Milan, Italy, in June 2004, with the proceedings published as volumes 2933 and 3365, resp- tively, of Lecture Notes in Computer Science. The pre-proceedingsof WMC6 were published by the Institute for Computer Languages of the Vienna University of Technology, and they were available d- ing the workshop. Conforming with tradition, this workshop, too, was a lively scienti?c event, with many questions and engaged discussions following pres- tations of papers. Thecurrentvolumeisbasedonaselectionofpapersfromthepre-proceedings. These papers were signi?cantly modi?ed according to the discussions that took placeduringtheworkshop, andalltheselectedpaperswereadditionallyrefe