The 6th International Conference on Medical Imaging and Computer-Assisted Intervention,MICCAI2003,washeldinMontr´ eal,Qu´ ebec,CanadaattheF- rmont Queen Elizabeth Hotel during November 15–18, 2003. This was the ?rst time the conference had been held in Canada. The proposal to host MICCAI 2003 originated from discussions within the Ontario Consortium for Ima- guided Therapy and Surgery, a multi-institutional research consortium that was supported by the Government of Ontario through the Ontario Ministry of E- erprise, Opportunity and Innovation. The objective of the conference was to o?er clinicians and scientists a - rum within which to exchange ideas in this exciting and rapidly growing ?eld. MICCAI 2003 encompassed the state of the art in computer-assisted interv- tions, medical robotics, and medical-image processing, attracting experts from numerous multidisciplinary professions that included clinicians and surgeons, computer scientists, medical physicists, and mechanical, electrical and biome- cal engineers. The quality and quantity of submitted papers were most impressive. For MICCAI 2003 we received a record 499 full submissions and 100 short c- munications. All full submissions, of 8 pages each, were reviewed by up to 5 reviewers, and the 2-page contributions were assessed by a small subcomm- tee of the Scienti?c Review Committee. All reviews were then considered by the MICCAI 2003 Program Committee, resulting in the acceptance of 206 full papers and 25 short communications. The normal mode of presentation at MICCAI 2003 was as a poster; in addition, 49 papers were chosen for oral presentation.