Description:This book constitutes the thoroughly refereed post-proceedings of the First International Workshop on Learning and Adaption in Multi-Agent Systems, LAMAS 2005, held in Utrecht, The Netherlands, in July 2005, as an associated event of AAMAS 2005. The 13 revised papers presented together with two invited talks were carefully reviewed and selected from the lectures given at the workshop. The papers increase awareness and interest in adaptive agent research, encourage collaboration between machine learning experts and agent system experts, and give a representative overview of current research in the area of adaptive agents.