The inhibitory deficit hypothesis of cognitive aging (Hasher & Zacks, 1988) holds that age-related declines in inhibitory function are responsible for many of the changes in cognitive functioning observed in aging. Eight experiments are proposed here to examine age differences in inhibitory function in the context of the negative priming paradigm. The phenomenon of negative priming depends on efficient inhibitory processes, and so allows the straightforward prediction that older adults should exhibit reduced negative priming, or even none at all. The literature, however, indicates that the picture is not quite so simple. Some studies observe age differences in negative priming and some have not. To deal with this state of affairs, a number of theories and models of selective attention, aging, and negative priming are beginning to appear. These models and theories offer quite different accounts of the processes underlying selective attention performance on a negative priming task. The experiments proposed here attempt to differentiate between the models with critical tests of predictions worked out for those models. The goal of this work is to narrow the field of possible explanations for the pattern of results reported in the literature, and in so doing contribute to our understanding of the mechanisms underlying age differences in selective attention. In addition, this work can contribute knowledge useful for ameliorating behavioral deficits experienced in later adulthood.