A random walk model of the classical mental rotation task is explored in two experiments. By assuming that a mental rotation is repeated until sufficient evidence for a match/mismatch is obtained, the model accounts for the approximately linearly increasing reaction times (RTs) on positive trials, flat RTs on negative trials, false alarms and miss rates, effects of complexity, and for the number of eye movement switches between stimuli as functions of angular difference in orientation. Analysis of eye movements supports key aspects of the model and shows that initial processing time is roughly constant until the first saccade switch between stimulus objects, while the duration of the remaining trial increases approximately linearly as a function of angular discrepancy. The increment results from additive effects of (a) a linear increase in the number of saccade switches between stimulus objects, (b) a linear increase in the number of saccades on a stimulus, and (c) a linear increase in the number and in the duration of fixations on a stimulus object. The fixation duration increment was the same on simple and complex trials (about 15 ms per 60°), which suggests that the critical orientation alignment take place during fixations at very high speed.