Using exposure-based treatment for fear of heights, we tested two different manipulations, namely administering blocks of exposure trials on an expanding spaced schedule and varying the nature of the exposure, both of which have been shown to reduce return of fear [Rowe, M. K., & Craske, M. G. (1998a). Effects of an expanding-spaced versus massed exposure schedule on fear reduction and return of fear. Behaviour Research and Therapy, 36, 701–718; Rowe, M. K., & Craske, M. G. (1998b). Effects of varied-stimulus exposure training on fear reduction and return of fear. Behaviour Research and Therapy, 36, 719–734.]. The samples for these two studies included 23 and 34 undergraduates, respectively. Fear was assessed before, immediately after and one month after treatment using self-report and physiological measures. Study hypotheses were not strongly supported, but the manipulations did lead to different responses during treatment. The data suggest that physiological habituation is not necessary for fear reduction. Expanding spaced treatment may have increased generalization, and those in the constant and varied conditions responded to different aspects of the exposure. Reasons for the failure to replicate previous research and ideas for future research are discussed.