On the one hand, the field of software product lines (SPLs), as described in the articles in this section, covers all the software development life cycle necessary to develop a family of products where the derivation of concrete products is made systematically and rapidly [10]. On the other hand, agent-oriented software engineering (AOSE) is a new software engineering paradigm that arose to apply the best practices in the development of complex multi-agent systems (MASs) by focusing on the use of agents, and organizations (communities) of agents as the main abstractions [7]. Following a somewhat slow start, agent technology has begun to come into its own. With the advent of biologically inspired, pervasive, and autonomic computing, the advantages of, and necessity of, agent-based technologies and MASs has become obvious. Unfortunately, current AOSE methodologies are dedicated to developing single MASs. Clearly, many MASs will make use of significantly the same techniques, adaptations, and approaches. The field is thus ripe for exploiting the benefits of SPLs: reducing costs, improving time to market, and enhancing agent technology in such a way that it is more industrially applicable. We believe there is much that can be achieved by combining the two approaches: applying the SPL philosophy for building a MAS will afford all the advantages of SPLs and make MAS development more practical. Thus, our intent in this article is twofold: to stress the feasibility and benefits of what we call multi-agent systems product lines (MAS-PL) and demonstrate the main research challenges in the development of MAS-PLs.