A great deal of research in the area of agent-oriented software engineering (AOSE) focuses on proposing methodologies for agent systems, i.e., on identifying the guidelines to drive the various phases of agent-based software development and the abstractions to be exploited in these phases. However, very little attention has been paid so far to the engineering process subjacent to the development activity, disciplining the execution of the different phases involved in the software development. In this paper, we focus on process models for software development and put these in relation with current researches in AOSE. First, we introduce the key concepts and issues related to software processes and present the various software process models currently adopted in mainstream software engineering. Then, we survey the characteristics of a number of agent-oriented methodologies, as they pertain to software processes. In particular, for each methodology, we analyze which software process model it (often implicitly) underlies and which phases of the process are covered by it, thus enabling us to identify some key limitations of currently methodology-centered researches. On this basis, we eventually identify and analyze several open issues in the area of software process models for agentbased development, calling for further researches and experiences.