This study, realized with the full collaboration of the artist, describes and reproduces over 300 posters designed by him, from 1927 through 2009 (when he celebrated his 100th birthday); it also reveals a number of projects that still remain in his studio. The catalogue was also published in a German language version. N.B. there also exists an earlier monograph on the posters: "Hans Erni : die Plakate = les affiches, 1929-1992" by the same author.