This article reports a generic methodology for developing health literacy assessment tools, consisting of 5 steps: (a) semi-structured, in-depth interviews of health care consumers; (b) consultation with health care, education, and psychometrics experts; (c) generation of an item pool; (d) selection of items for inclusion in the Mandarin Health Literacy Scale; and (e) evaluation of readability. To illustrate, the authors applied the methodology in order to develop a health literacy scale for the Mandarin Chinese-speaking population. They field-tested the initial version of the scale with a random sample of 323 Taiwanese adults. In addition, the authors used item response theory and classical test theory to examine the psychometric properties of the scale. Results showed good validity and reliability.