Welcometothe6thInternationalWorkshoponPassiveandActiveMeasurement, held in Boston, Massuchusetts. PAM 2005 was organized by Boston University, with ?nancial support from Endace Measurement Systems and Intel. PAM continues to grow and mature as a venue for research in all aspects of Internet measurement. This trend is being driven by increasing interest and activity in the ?eld of Internet measurement. To accommodate the increasing interest in PAM, this year the workshop added a Steering Committee, whose members will rotate, to provide continuity and oversight of the PAM workshop series. PAMplaysaspecialroleinthemeasurementcommunity. Itemphasizespr- matic, relevant research in the area of network and Internet measurement. Its focus re?ects the increasing understanding that measurement is critical to e?- tive engineering of the Internet’s components. This is clearly a valuable role, as evidenced by the yearly increases in the number of submissions, interest in, and attendance at PAM. PAM received 84 submissions this year. Each paper was reviewed by three or four Program Committee (PC) members during the ?rst round. Papers that received con?icting scores were further reviewed by additional PC members or external reviewers (typically two). After all reviews were received, each paper with con?icting scores was discussed extensively by its reviewers, until a c- sensus was reached. The PC placed particular emphasis on selecting papers that were fresh and exciting research contributions. Also, strong preference was given to papers that included validation results based on real measurements.