Project Abstract The size of the lesbian, gay, bisexual and transgender (LGBT) population is estimated to be between 9 and 11 million (3.5–4.5%). The LGBT population has been identified as having poorer health than their non-LGBT peers on many dimensions. Although we know less about older LGBT adults, they are of special interest since chronic disease and disabilities increase with age and disparities often emerge or widen, making older LGBT adults an at-risk population. The National Academy of Medicine (NAM) has issued two reports on the state of LGBT health, both of which call for more targeted research aimed at understanding the sources and consequences of these health disparities, particularly among older LGBT adults. A representative national study of older LGBT adults would permit the type of work recommended by the NAM committee. The purpose of the current Sampling Strategies and Measure Development for the LGBT Aging Project (SAMLAP) is to develop and evaluate a platform and a process that will permit the execution of a future, separately-funded national probability-based longitudinal study of aging in the older LGBT population (the National LGBT Aging Project (NLAP)). Our specific aims are: (1) to develop and implement a strategy to identify and recruit a probability sample of LGBT older adults; (2) to compare and evaluate the effectiveness of the screening strategy and the quality of the resulting sample, using the results of the randomized experiments as appropriate; (3) to identify and develop survey measures of social relationships and experiences appropriate for use in the future National LGBT Aging Project (NLAP) and administer these via 300 follow-up interviews in households identified as containing at least one LGBT older adult; and, (4) conduct a controlled randomized field test of in-home versus remote interviewing for the follow-up interviews, using a sequential adaptive design that will permit a robust comparison of response rates, differential nonresponse bias, and costs. The product of this work will be a sampling methodology, screening process, set of measures, and field approach—optimized where appropriate through randomized experiments—tailored to conduct the first ever U.S. national study of LGBT older adults using an address-based probability sample with a high response rate (NLAP), to be submitted separately based on the results of this application. NLAP will permit inference to the population of LGBT individuals as well as the population of partnerships involving at least one LGBT individual; it will answer critical health and policy questions concerning LGBT individuals, as well as enhance our methods for studying and understanding issues involving the health and aging of all Americans.