Validation provides quality assurance that a hearing aid wearer’s needs are being met—that the solution meets not only their technical requirements (i.e., verification) but also their requirements for everyday communication. In the past 50 years, there have been repeated calls for better measures of hearing aid performance, with a general shift in validation toward the self-report of hearing, communication, and well-being through questionnaires. This chapter looks at these measures, examining the domains of hearing aid validation and how despite the growth in number of questions—a total of more than 1,000 questions on hearing aids—the domains have evolved only slightly. The chapter then considers the ways in which a fundamental domain, “benefit,” is calculated. A large data set shows how different forms of benefit can lead to different systematic interpretations. While most objective measures for hearing aids are by definition verifications, the chapter discusses those objective measurements that approach validation by attempting to mimic aspects of everyday communication. The issues raised by these myriad forms of validation suggest that a viable measure of hearing aid benefit must incorporate measures of expectations and burdens for listener-specific conditions.