In this paper, a magnetorheological (MR) torque transfer device is designed, modeled, and controlled. MR fluids possess the unique ability to undergo dramatic and nearly completely reversible changes in their rheological properties under the application of a magnetic field. These controllable fluids can serve as quiet, rapid interfaces between electronic controls and mechanical systems. One area of application is to use these fluids as actuators. The MR torque transfer device can function as either a clutch or a brake. This coupling device was designed and built using a parallel plates configuration, and uses a stationary electromagnetic coil to activate the fluid. A PID controller is designed and experimentally evaluated. In the experimental control setup, the output variables are the position, velocity, and torque at the output shaft and the control input is the electromagnet current. Angular position of the output shaft and the transferred torque are measured using an encoder and a torque transducer, respectively. A dSpace control system was used to experimentally implement the control algorithms. The closed loop performance of system was studied for both torque regulation as well as torque tracking.