This study comprises 4 phases designed to systematically develop and test a reliable, valid and useful quantitative measure of the components and dimensions of yoga; each phase builds on the previous phase. Phase I aims to gain a comprehensive understanding of the relevant aspects of yoga therapy and develop a large pool of potential questionnaire items by conducting a thorough literature review and focus groups with yoga teachers and students. These data will be analyzed using rigorous qualitative methods to identify key conceptual dimensions associated with yoga interventions. Phase II will develop a prototypic questionnaire to assess yoga therapy by refining and honing information from Phase I and conducting cognitive interviews to further develop this instrument. Phase III will pilot test the measure in a field observation of yoga students and use factor analysis and item response theory to select the best items per dimension and to reduce the number of items in the measure. Phase IV will collect data on the new instrument and test the psychometric properties of the questionnaire (i.e., reliability and validity using data collected in Phases III and IV).