In this chapter a series of experiments are described where large-amplitude gaze shifts were recorded in the head-free condition, and eye saccades in the head-fixed condition. The amplitude of head-fixed saccades was chosen in order to correspond to the amplitude of the eye movements in the orbit in head-free condition. By comparing head-free and head-fixed eye saccades of equivalent size, vestibulo-ocular reflex (VOR) gain changes during large gaze shifts involving both the eye and the head can be indirectly measured. Quantification of the VOR gain variations during large gaze shifts has been done by a systematic comparison of saccade dynamics in head-free and head-fixed human subjects, under certain conditions, such as identical eye saccade amplitude and starting position. This analysis is only possible when the head velocity attains a sufficient level, and is thus reserved for the terminal part of the gaze shift. In addition, the validity of the estimation of the VOR gain and of the hypotheses proposed to explain the observations has been tested by model simulations.