This book is the eighth in the successful line of Intelligent Agents books published in LNAI. It is based on the Eighth International Workshop on Agent Theories, Architectures, and Languages, ATAL 2001, held in Seattle, WA, USA, in August 2001. The 31 revised full papers presented together with an overall introduction and two special session overviews were carefully reviewed and selected during two rounds of improvement from 68 submissions. The papers are organized in topical sections on agent modeling; formal specification and verification of agents; agent architectures and languages; agent communication; collaborative planning and resource allocation; trust and safety, formal theories of negotiation; and agents for hand-held, mobile, or embedded devices.