Abstract. Today's software systems rely heavily on complex resources, such as humans. Human-intensive systems are particularly important in our society, especially in the healthcare, financial, and software development domains. One challenge in developing such systems is that the system design must account for the constraints, capabilities, and allocation policies of their complex resources, particularly the humans. The resources, their capabilities, and their allocation policies and constraints need to be carefully specified, and modeled. Toward the goal of supporting the design of systems that make effective use of such resources, we introduce a resource specification language and a process-aware, discrete-event simulation engine that simulates system executions while adhering to these resource specifications. The simulation supports (1) modeling the resources that are used by the system, and the ways in which they are used, (2) experimenting with different resource capability mixes and allocation policies, and (3) identifying such undesirable situations as bottlenecks, and inefficiencies that result from these mixes and policies. The joint use of detailed resource specifications and simulation supports rapid evaluation of human-intensive system designs. We evaluate our specification language and simulation framework in the healthcare domain, on a software system for managing a hospital emergency department.