Most medical organizations recommend informed decision making before undergoing prostate cancer screening. The authors conducted a detailed evaluation of men's use of an interactive, Web-based prostate cancer screening decision aid. Participants (N = 531) were 57 years old (SD = 6.8), 37% were African American, and 92% had Internet access. Men completed 2 telephone interviews, pre- and 1-month post-Web site availability. Half of the sample (n = 256) accessed the Web site. Multivariate analysis revealed that users were more likely than nonusers to be White (OR = 2.37, CI 1.6-3.6), previously screened (OR = 2.13, CI 1.07-4.26), have Internet access (OR = 3.66, CI 1.15-11.58), and to report daily Internet use (OR = 2.58, CI 1.47-4.55). Agreement between self-reported and actual Web site use was moderate (κ = .67). Tracking software revealed a mean of 1.3 (SD = 0.5) log-ons and a median of 38 min per log-on. Of participants, 84% used the values clarification tool, and more than 50% viewed each video testimonial. Baseline screening preference was associated with values clarification tool responses and Web site feedback. This study revealed that, beyond the digital divide, Web site use depended on more than Internet access. Further, electronic tracking of Web site use demonstrated overestimation of self-reported use, high use of interactive features, and effect of baseline screening preference on men's response to the Web site.