Although tailored print materials (TPMs) have been assessed for a variety of behavioral targets, their effectiveness as decision aids for genetic testing had not been evaluated at the time this study began. We compared TPMs and non-tailored print material (NPMs) that included similar content about genetic testing for breast and ovarian cancer susceptibility. TPMs were prepared especially for an individual based on information from and about her. We mailed baseline surveys to 461 women referred by physicians or identified through a tumor registry. All had personal and family histories of breast and/or ovarian cancer and, on the basis of these histories, an estimated > or =10% probability of carrying a mutation in the breast/ovarian cancer genes BRCA1 or BRCA2. The 325 (70%) who responded were randomly assigned to receive TPM or NPM. Followup surveys, mailed 2 weeks following receipt of print materials, were returned by 262 women (81% of baseline responders). Participants were predominately white (94%) and well-educated (50% college graduates). The mean age was 49 years. At follow-up, TPM recipients exhibited significantly greater improvement in percent of correct responses for the 13-item true/false measure of knowledge (24% increase for TPM vs. 16% for NPM; p < 0.0001) and significantly less over-estimation of risk of being a mutation carrier (40% TPM group overestimated vs. 70% NPM; p < 0.0001). Anxiety did not differ significantly between groups. Reactions to materials differed on two items: "seemed to be prepared just for me" (76% TPM vs. 52% NPM; p < 0.001) and "told me what I wanted to know about BRCA1 and 2 testing" (98% TPM vs. 91% NPM; p < 0.05). TPMs showed an advantage in increasing knowledge and enhancing accuracy of perceived risk. Both are critical components of informed decision making.