The scope of this paper is to investigate the practical application of using either ferro- or magnetorheological fluids to actively control the fluid flow, pressure generation, and dynamic behavior of a hydrodynamic bearing. Further, this study will endeavor to establish, on a comparative basis, the suitability of each one of these two fluids for use with and control of a self-acting bearing when speed, eccentricity, and the applied magnetic field are changed parametrically. Both ferro- and magnetorheological may provide active control when subject to a magnetic field, but through different mechanisms: the ferrorheological through a discrete change in the body force, while the magnetorheological through global change in its dynamic viscosity. Regardless, changes caused in the ferro- or magnetorheological properties affect the pressure distribution, load-carrying capacity, and frictional torque. By influencing the load-carrying capacity, torque, and attitude angle on a timely basis, as a machine moves transiently from one operational regime to another, one can both extend the operational envelope of the bearing and provide much needed health monitoring protocols for the device (e.g. gas or steam turbine, compressor, etc.).