This volume contains 56 contributions presented at the 1st International Symposium on Post-Translational Modifications of Proteins and Ageing, held on the Island of Ischia (Naples, Italy) from May 11 to 15, 1987, under the auspices of the University of Naples and the Italian Society of Biochemistry. The primary aim of this interdisciplinary meeting was to promote a productive exchange among scientists from different cultural areas, and to give them the opportunity to discuss problems of common interest approached from different scientific standpoints. Although a large number of studies has led to a definition of the chemical mechanisms and of the main enzymological aspects of the several post-translational modifications of proteins, we are still far away from a complete elucidation of the functional significance of such processes. As a matter of fact, it seems reasonable that the presently available experi­ mental approaches and models employed to investigate the biological roles are still inadequate. The search for suitable model systems was a matter of discussion during the meeting, and will be a major challenge in the future. The most frequently employed approaches to this problem thus far have been in vitro, but several proteins reported to be excellent in vitro substrates failed to show any activity when assayed in in vivo models.