This article tested the ability of the theory of planned behavior (TPB) to predict patterns of behavior change associated with health screening. Attitudes, subjective norms, perceived behavioral control, and intentions were used to predict objective measures of attendance 1 month and 13 months later among participants who had never previously been screened (N = 389). Findings showed that the TPB predicted attendance on each occasion and also predicted frequency of attendance. However, the model was unable to reliably distinguish among consistent attendees, participants who delayed attending, and participants who initially attended but relapsed. Thus, the TPB needs to be extended to understand behaviors that must be performed promptly and repeatedly for health benefits to accrue.