Prevention is better than cure, but very little is known on effective prevention of anxiety disorders. Individuals vulnerable for trauma-exposure would benefit from effective techniques to prevent the development of post-traumatic stress. One reason for the apparent standstill in this literature may be the exclusive focus on the development of fear, while pre-clinical anxiety treatment research has turned to impaired extinction of fear as the main mechanism underlying abnormal anxiety. Conditioning theories propose latent inhibition as a technique to prevent the development of fears, but the effects on fear extinction have not been examined in detail. I conducted two experiments to evaluate the effects of latent inhibition on extinction in a standard human fear conditioning paradigm, which serves as a model for post-traumatic stress disorder. Skin conductance reactivity and online expectancy ratings revealed slower rates of fear acquisition in the latent inhibition groups, as well as a speeded extinction effect early in extinction. However, extinction of expectancy ratings was less complete in the latent inhibition groups. The beneficial effects of the latent inhibition technique may be in promoting early success of self-exposures or exposure treatment and motivating the patient to continue on the exposure path.