The present dissertation explored the function and mechanisms of inhibition of return (IOR), an orienting phenomenon characterized by slower responses to targets appearing at previously cued than to uncued locations. The key findings are: (1) With improved methodology, the present thesis explored IOR in visual search with a probe-following-search paradigm and the results supported the use of relatively small set size. (2) Supporting the proposition that IOR functions as a foraging facilitator in visual search (Klein, 1988; Klein & Macinnes, 1999), IOR effects were observed following static and slow dynamic search tasks but not for a fast dynamic search task (Horowitz & Wolfe, 1998) in which memorial mechanisms were rendered useless by randomly exchanging item locations. (3) A strong focussed attention at fixation eliminated IOR in a cue-target paradigm, suggesting that the behavioral manifestation of IOR can be modulated by attentional control settings. (4) Simulations in a dynamic neural field (DNF) model of the superior colliculus (Trappenberg, Dorris, Munoz, & Klein, 2001) reproduced the observation that saccades which reverse their vectors are slower to initiate than those which repeat vectors. This finding suggests that IOR effects observed in the saccade-saccade paradigms and the overt probe-following-search paradigm (Klein & Macinnes, 1999) are caused, or at least, contributed by a motor mechanism implemented in the superior colliculus. (5) Two mechanisms, sensory and motor, were proposed to explain IOR effects in the oculomotor system. Empirical observations confirmed that these two mechanisms have additive behavioral effects.