We developed a computer-based tailored risk presentation and risk communication aid for colorectal cancer prevention. To evaluate the effectiveness of the tool, we randomized 353 participants to receive different risk presentation formats (relative plus absolute risk vs. absolute risk only vs. none) and different levels of engagement with the risk communication (active vs. passive). Findings suggest the tool to be useful for correcting misperceptions about personal risk. Of those with inaccurate risk perception at baseline, more than half of the participants in intervention groups had corrected risk perceptions at post-test, compared to only 12% in the control group.