This chapter provides the terminology and design types for mixed-methods studies, and covers benefits and barriers of mixed-methods approaches. It presents gerontological applications and examples of designs using this "third method" in the real world. True mixed-methods designs are defined along with designs that approximate mixed methods but are not true mixed-methods designs. Characteristics of good mixed-methods design are detailed. The chapter reviews each design type (explanatory sequential, exploratory sequential, convergent parallel, embedded, transformative, and multi-level) along with a decision-making process for selecting each design, and explains nomenclature and sampling options. Steps are provided for general data analysis methods and design-specific data analysis designs. The chapter concludes with ways to integrate findings from the quantitative and qualitative aspects of a mixed-methods design. Unique mixed-methods terminology for reliability and validity (legitimization and inference transferability, or applying results to other settings) is covered.