The metaphors of of autonomous agents and agent societies have the potential to make a significant impact on the processes of analysis, design, and development of complex software systems on the Internet. In this chapter, we concentrate predominantly on agent societies, and show how work on coordination models and technologies provides a powerful framework for the engineering of Internet-based, multi-agent systems. First, we introduce the concepts of agent, multi-agent system, and agent-oriented software engineering, and highlight the specific issues that arise when we take the Internet as the environment that agents inhabit. We then provide a brief survey of the state of the art in the area of agent-oriented methodologies, paying particular attention to the Gaia methodology for agent-oriented analysis and design. Gaia was originally conceived for benevolent agents inhabiting closed systems. However, to broaden its scope, we show how insights from the area of coordination models can be incorporated in order to make it more suitable for developing Internet-based applications.