This volume is based on papers presented at the5thWorkshoponM- brane Computing, WMC5, which took place in Milan, Italy, in the period June 14-16, 2004, as a satellite event of DNA10 (10th International Workshop on DNA-Based Computing). The ?rst three workshops were organized in Curtea de Arge, s, Romania - they took place in August 2000 (with the proceedings p- lished in Lecture Notes in Computer Science, volume 2235), in August 2001 (with a selection of papers published as a special issue ofFundamenta Inform- icae, volume 49, numbers 1-3, 2002), and in August 2002 (with the proceedings publishedinLectureNotesinComputerScience,volume2597).Thefourthwo- shop took place in Tarragona, Spain, in July 2003 (the proceedings appeared as volume 2933 of Lecture Notes in Computer Science). Like the previous two meetings, also WMC5 was an o cial workshop of the Molecular Computing Network (MolCoNet) funded by the EU Commission in theFifthFrameworkprogramInformationSocietyTechnologies(projectnumber IST-2001-32008). The preproceedings of WMC5 were published as a MolCoNet report, and they were available during the workshop. This volume contains only a selection of the papers from the preproceedings.
