This volume contains the proceedings of the vVorkshop on Trees held in Versailles on 14-16 June 1995. Why: a workshop on trees? Two main reasons motivated this workshop. First, the current plethora of tree representations in branching processes which has be- come obvious by the Minneapolis IMA Congress Classica] and Modern Branching Processes in 1994. But this would not have been sufficient to organize an "n-th" congress on branching processes. Secondly, regular discussions with researchers in algebra and computing sciences at the University of Versailles and at INRIA (lnstitut National de...