Welcome to the Thirteenth ACM International Conference on Multimedia (ACM MM 2005) held in Singapore from 6 - 11 November 2005 at the Hilton Hotel. ACM Multimedia is the premier academic conference in multimedia. The series started in 1993, at the start of multimedia era, and has quickly developed into the top conference in the field. Over the years, the concept of multimedia has evolved, from research in separate "non-textual" media such asimage, video and audio in the early years, to truly "multimedia" approaches integrating information of multiple medium types, including text and metadata, in recent years. Today, the conference covers a wide range of topics on the foundations of multimedia, aswell as multimedia applications, content and system. The pervasive use of multimedia has permeated into almost every aspect of our life. This is reflected in a wide variety of programs incorporated into the conference. The conference features the usualhigh-quality technical paper presentations, short poster paper presentations, doctoral symposium for senior graduate students, brave-new emerging topics, as well as tutorials and workshops invarious topical areas. One key aspect of this conference that is different from most other academic conferences is its emphasis onsystems and applications. To this end, the conference also includes technical demonstrations of research prototypes and systems, open software competition, video demonstration of concepts and applications, as well as interactive arts which includes an exhibition of multimedia art. The interactive arts program, started in ACM MM 2004, is well integrated into the main activity of the conference this year. The main technical program achieves a balance between theory and practice in applications, content and systems research in multimedia. This year we received 312 papers in three tracks: Applications (98 submissions), Content (150 submissions) and Systems (64 submissions). Each paper was reviewed by three reviewers in a double-blind review process. The program committeemet on 23 June 2005 in Beijing to select the papers to be presented at the conference. The rigorous review process has culminated into the acceptance of 49 papers: 15 in Applications track, 24 in Content track, and 10 in Systems track. This represents an acceptance ratio of 16%. We would like to thank the program committee and the technical program co-chairs, Mohan Kankanhalli, Lynn Wilcox, and Ralf Steinmetz, for a difficult job well done. This year we received a record number of over 200 submissionsfor the short paper track co-chaired by Chitra Dorai, Kiyoharu Aizawa and Roger Zimmermann. This is an increase of 28% over last year's submission. With hindsight of last year's experience, theco-chairs had pro-actively set up a program committee to handle the anticipated load. Thus despite the high load and short review cycle of about one month, the review process had been smooth andrigorous. The committee accepted 59 papers from the submitted papers. This, together with another 11 papers recommended from the full paper track, results in a high quality set of short papers. All credits must go to the short paper program committee and co-chairs for doing an outstanding job. Another track that has grown steadily and has gained a special foothold in this conference is the interactive arts program. Under the guidance of co-chairs Alejandro Jaimes, Andrew Seniors and Wolfgang Muench, the group set out to attract quality submissions for full, short as well as exhibition papers for this program. The publicity and subsequent review process have culminated into the acceptance of 9 full papers, 12 short papers, and 16 exhibits. These papers are integrated into the main program for the conference. In particular, a 7-day exhibition of interactive multimedia arts will be held in conjunction with this conference at the art gallery of the Lasalle-SIA College of the Arts in Singapore. The exhibition will be open to the main conference participants, as well as the art fraternity and the public. It willgo a long way towards balancing technology and arts, and bringing in creative entertaining elements of multimedia arts to this community and the public. Special thanks must be given to theprogram committee and co-chairs for succeeding in undertaking such a difficult task.