Learn about the techniques used to create weights for the 2021 National Survey on Drug Use and Health (NSDUH) at the pair and questionnaire dwelling unit (QDU) levels. NSDUH is designed so that some of the sampled households have both an adult and a youth respondent who are paired. Because of this, NSDUH allows for estimating characteristics at the person level, pair level, or QDU level. This report describes pair selection probabilities, the generalized exponential model (including predictor variables used), and the multiple weight components that are used for pair or QDU levels of analysis. An evaluation of the calibration weights is also included.Chapters:Introduces the report.Discusses the probability of selection for pairs and QDUs.Briefly describes of the generalized exponential model.Describes the predictor variables for the model calibration.Defines extreme weights.Discusses weight calibrations.Evaluates the calibration weights.Appendices include technical details about the model and the evaluations that were performed.