Rotary left ventricular assist devices (LVADs) have greatly improved the outcomes and quality of life of patients with heart failure. However, rotary LVADs, when operated at a set speed, may result in over- or underpumping, leading to ventricular suction or venous congestion. This chapter discusses physiological control of rotary LVADs, systems that automatically adjust LVAD output based on changes in the state of the circulatory system. Such systems aim to adjust speed based on measurements (or estimation) of hemodynamic variables such as flow, pressure, or a combination of these. This chapter also summarizes methods of measuring and estimating hemodynamic variables that can be used to implement these systems in clinic. While significant development in this field has occurred over the last two decades, physiological control systems are still yet to be applied clinically.