This book presents the revised and expanded version of the 11 papers selected for presentation at the First International Workshop Declarative Agent Languages and Technologies, DALT 2003, held in Melbourne, Australia in July 2003 during AAMAS, also included are three invited papers by leading researchers in the area to ensure that competent coverage of all relevant topics. Papers were arranged in topical sections on Software-engineering and prototyping MAS - Agent reasoning, BDI logic, and extension - The social aspect of multi-agent systems