This volume presents the proceedings of the conference "Galaxy Disks and Disk Galaxies", sponsored by the Vatican Observatory. The meeting was held in Rome from 12 to 16 June, 2000, the Jubilee Year, a special year for the Catholic Church. The venue of the meeting was the Pontifical Gregorian University, a descendant of the former Roman College where Jesuit astronomers and mathematicians made significant contributions to the astronomy of that time. The meeting hosted about 230 participants coming from 30 countries. Social events included a visit of the Vatican Observatory and the Papal Villas at Castel Gandolfo. The very full program consisted of 29 review papers, 34 invited talks, and more than 180 posters. The posters were exhibited in a beautiful and spacious eighteenth century hall nicely located between the meeting room and the refreshment area. The conference covered topics regarding the structure, formation and evolution of galaxies with disks. Particular attention was dedicated to the stellar and gaseous disk of the Milky Way, the global characteristics of galaxy disks, their structure, morphology and dynamics, the gaseous components, star formation, and chemical evolution, the interactions, accretion, mergers and starbursts, the dark and luminous matter, the establishment of the scaling laws, and the formation and evolution of disk galaxies from a theoretical and observational point of view. The sections of this book reflect the meeting sessions. As pointed out in the Conference Summary, galaxies are the cross roads of Astronomy because they look up to Cosmology and they look down to the interstellar medium and star formation. This meeting highlighted the points of convergence in our comprehension of the formation and properties of disk galaxies, suggesting at the same time that the future challenges in this field are to make those connections (such as between the properties of hydrodynamical models and those of real galaxies or between a physically based theory of star formation and what is observed in galaxies) that at the moment we have failed to make.