Thinkhealth is a risk assessment tool and Website to promote screening and early detection of breast cancer among the general population. Interactive features include a personalized risk assessment based on the Gail model, and a screening plan based on the user’s health history. Direct links to screening facilities connect patients with providers, and on-line scheduling simplifies appointments. An "Ask the Doctor" feature facilitates patient-physician communication. Website design was based on the principles of cognitive learning in the Human Dynamics model, and the user’s online experience is tailored to specific cognitive styles. This enables us to communicate with the user in the style most appropriate to her personality and learning style. We measured the effectiveness of this Website in motivating screening intentions and behaviors among 750 women and found that thinkhealth.com was more effective than printed material in educating women on screening techniques, reducing anxiety about mammograms, and strengthening intentions to maintain a screening regimen. Funding for development was provided by the National Institutes of Health, National Cancer Institute.