This chapter studies the microeconometric treatment-effect and structural approaches to dynamic policy evaluation. First, we discuss a reduced-form approach based on a sequential randomization or dynamic matching assumption that is popular in biostatistics. We then discuss two complementary approaches for treatments that are single stopping times and that allow for non-trivial dynamic selection on unobservables.The first builds on continuous-time duration and event-history models.The second extends the discrete-time dynamic discrete-choice literature.