"Hors-Sol" is a record of poster actions conducted by fine artists in public places in Switzerland, starting with the sensational campaign mounted by the Zurich Concrete Artists in 1961. Though the poster is usually a medium for commercial messages, here it is used to convey new meanings, some firmly anchored in the context of art, others explicitly aimed at advertising. Disturbing intrusions into everyday life, these visual actions cause people to reflect on the condition in which art and PR function. In historical comparison, they function as a mirror of the time and reveal a great deal about changing social conditions. The poster campaigns that took place in the 1960s and 80s were impressively explosive and alarmingly direct, whereas today's artistic forays into the poster as medium are evidence that PR aesthetics and the art world are becoming more and more indistinguishable.