An overview and critique of research measures of inappropriate psychoactive drug use in the treatment of frail older adults is presented. These measures are compared on the basis of six key criteria for the complex determination of inappropriate psychoactive drug use as a research variable. These six instruments/standards are examined also for their advantages and disadvantages as research tools. Based on this review and related literature, recommendations are made that future studies of inappropriate psychoactive drug use include expert clinician assessment, measures of target symptoms and functional status, physiological indicators wherever possible, and drug and dosage classifications according to interdisciplinary consensus-based criteria.