High-speed planing craft slamming into waves can cause structural damage to the vessel as well as hinder or injure personnel onboard. As a result, it is one of the primary constraints that limit the operating envelope of high-speed surface vessels. The controlled motion experiments presented in this thesis were designed to be an intermediate step between vertical water entry tests of a wedge and a traditional tow tank experiment of a planning hullform in waves. This allowed a deeper study of the hydrodynamic loads that occur during slamming. A planing hull model was subjected to controlled motions in the vertical plane to replicate the types of slamming motions that a vessel may experience in the ocean. The slamming events investigated were chosen based on towing tank experiments previously conducted at the U.S. Naval Academy. Hydrodynamic forces were measured globally and also at particular locations near the bow. The vertical motions were programmed into a pair of linear actuators that were rigidly mounted to the towing carriage. The towing carriage prescribed the horizontal motion. Each actuator was independently controlled and capable of moving at 1.3 m/s and 15 m/s^2. Pressure sensors were used to measure the pressure time history at discrete points on the model. Force sensors mounted beneath the actuators were used to compute the overall slamming load and moments induced by the slam event. A combination of other sensors were used to verify the accuracy of the prescribed motion profile. The results suggested that total impact velocity is correlated with the load growth rate. In addition, the velocity normal to the keel was found to be most impactful on the magnitude of the peak force. / Master of Science / The goal of this thesis was to understand the effect of high-speed boats impacting waves. These wave slamming events can harm the boat and make people sea sick onboard. Consequently, the top speed at which these high-speed boats can operate safely is often limited by these wave impacts. The approach taken for this study involved using a model boat that had similar features to high-speed boats seen in the real world. The model underwent specific movements to replicate the impact that occurs when a real boat encounters waves at sea. This method sought to identify important parameters that determine the severity of the slam event. A Vertical Planar Motion Mechanism simulated the slamming motion, allowing the model boat to move at high speeds relative to its size. A variety of sensors located throughout the model collected data on the slam event. The combination of these sensors helped paint a picture of what is occurring during the entire slam event. This study focused on the dynamics that are measured by the sensors. This included the pressure at important locations, the force on the whole model, and the way that the model moves. The Office of Naval Research provided both financial and intellectual support that makes this research possible. Beyond the ONR, many other academic, commercial, and military groups had given their support for this work.