One of the functions of the vestibular system is to engage neural reflexes, which ensures the stabilization of a visual image during head movements. This is accomplished through the stimulation of vestibular hair cells, which respond to accelerations, and then produce compensatory eye movements opposing head motion. This called the vestibulo-ocular reflex (VOR). Hair cell loss results in vestibular deficits, and for these individuals, this loss of function is debilitating and results in vertigo and decreased visual acuity. To address these deficits, the Phillips lab has developed a vestibular prosthesis, which aims to use electrical stimulation to restore function by artificially activating individual branches of the vestibular nerve. However, it is not known precisely how the system changes after hair cell loss; this may have implications for the effectiveness of the prosthesis in treating vestibular loss. To explore this, we examined the interaction between the electrical activity and residual vestibular activity after vestibular loss. We first introduced a vestibular deficit in a rhesus macaque through successive gentamicin injections into the middle ear to destroy vestibular hair cells, and measured VOR responses to verify the progressive vestibular loss. Next, we recorded eye velocities in response to electrical stimulation to characterize changes in the efficacy of stimulation, thus providing insight into the prosthetic mechanism. Finally, modulated electrical stimulation was provided during rotation of the rhesus macaque to test the efficacy of the prosthesis in restoring VOR in conjunction with residual vestibular activity. Characterizing prosthetic function during increasing vestibular deficit is important in determining the mechanism of stimulation, the physiological responses succeeding hair cell loss, and ultimately a model for the prosthetic efficacy for human patients.