PURPOSE: To use a mixed-methods approach to develop a letter that can be used to notify patients of their bone mineral density (BMD) results by mail that may activate patients in their bone-related health care. PATIENTS AND METHODS: A multidisciplinary team developed three versions of a letter for reporting BMD results to patients. Trained interviewers presented these letters in a random order to a convenience sample of adults, aged 50 years and older, at two different health care systems. We conducted structured interviews to examine the respondents' preferences and comprehension among the various letters. RESULTS: A total of 142 participants completed the interview. A majority of the participants were female (64.1%) and white (76.1%). A plurality of the participants identified a specific version of the three letters as both their preferred version (45.2%; P<0.001) and as the easiest to understand (44.6%; P<0.01). A majority of participants preferred that the letters include specific next steps for improving their bone health. CONCLUSION: Using a mixed-methods approach, we were able to develop and optimize a printed letter for communicating a complex test result (BMD) to patients. Our results may offer guidance to clinicians, administrators, and researchers who are looking for guidance on how to communicate complex health information to patients in writing.