Magnetorheological (MR) and electrorheological (ER) materials show variations in their rheological properties when subjected to varying magnetic and electric fields respectively. They have quick time response, in the order of milliseconds, and thus are potentially applicable to structures and devices when tunable system response is required. When incorporated into an adaptive structural system, they can yield higher variations in the dynamic response of the structure. This study presents a detailed analysis of vibration control capabilities of adaptive structures based on MR and ER materials, and compares their vibration minimization rates, time responses, and energy consumption rates. Homogenous one-dimensional MR and ER adaptive beam configurations were considered. Structural dynamic modeling approach was discussed, and vibration characteristics of MR and ER adaptive beams were predicted for different magnetic and electric field levels. In addition to the model predictions, actual MR and ER adaptive beams were fabricated and tested. Both studies illustrated the vibration minimization capabilities of the MR and ER adaptive beams at different rates and environmental conditions. The relative performances of both MR and ER adaptive beams were discussed in detail and their advantages and disadvantages were listed.