Background: Few instruments exist that measure knowledge of osteoporosis, a health risk for 28 million Americans. The original Facts on Osteoporosis Quiz (FOOQ), which was theoretically informed by Orem's (1995) Self-Care Theory, was published in 1998. In 2000, the National Institutes of Health (NIH) held a consensus conference on osteoporosis in which previous knowledge was modified based on current science. Objectives: The goal was to update the original instrument based on the latest scientific evidence and to determine its psychometric properties. Method: The quiz content was validated by osteoporosis experts and is theoretically informed by Orem's (2001) Self-Care Theory. An iterative process was used to design an instrument with an acceptable reading level. Reliability, item discrimination, and item difficulty were assessed in a convenience sample of 256 participants. Results: The revised quiz, content-based on the 2000 NIH osteoporosis consensus conference, includes 20 questions. The quiz has a content validity index of .87, an internal consistency reliability of .76 and a 6th grade reading level. Item difficulty and item discrimination are also reported. Conclusions: The revised version of the FOOQ provides a valid, reliable, and theoretically informed instrument with acceptable psychometric properties.