In the execution of an activity instance (also called work item) in a business process, the first step is to determine who will execute this activity instance, i.e., assign one or more actors to the work item. Proper actor assignment heavily contributes to the effective and efficient execution of a business process - and of the entire organization that holds the process. If actor assignment is dynamic, it contributes to the agility of organizations required in times of digital transformation. This chapter explains how work items can be automatically assigned to the actors in a business process that is supported by a BPMS. First, the basic notion of actor assignment is explained, after which more advanced mechanisms to select and allocate an actor are discussed. Although much of these advanced notions are only conceptual developments so far, we also discuss a few preliminary applications of advanced dynamic actor assignment in various domains. These applications illustrate the broad possibilities and potential of advanced dynamic actor assignment to improve process execution in various dimensions.