This report describes changes in the 2014 and 2015 NSDUHs that were designed to increase the efficiency of data collection and processing and to improve the quality of the data collected. In 2014, changes were made in the sample sizes allocated to each state and to different age groups in order to increase the precision of national and many state estimates as well as estimates for older adults. In 2015, changes were made to the survey questionnaire to improve the quality of the data collected, expand the number of prescription drugs covered, and address changing substance use and mental health policy and research needs. New data collection equipment was introduced in 2015 to replace the older equipment in the field. Respondent materials also were updated. This report provides information on the key changes made as well as some of the potential implications for data users.