This article examines the perceptual consequences of activating illness concern as a function of hypochondriacal tendencies. In 2 independent samples, hypochondriacal tendencies were associated with slower reaction times on a modified emotional Stroop task when the stimulus words were illness related, but only when illness concern was activated. Moreover, these findings emerged when hypochondriacal tendencies were defined as a sensitivity to bodily sensations. When defined as illness preoccupation and fear, hypochondriacal tendencies were associated with a generalized pattern of perseveration to all stimuli when health concern was activated. Finally, the results persisted even after statistically controlling for state anxiety. Findings are discussed within the context of an activation hypothesis and highlight the importance of the operational definition and assessment of hypochondriacal tendencies when examining perceptual biases.