Recent research has highlighted the importance of investigating the efficacy of psychotherapeutic interventions for individuals with physical health conditions. To date, there is evidence that psychotherapeutic interventions are efficacious for a range of physical health conditions (e.g., cancer, obesity, and diabetes). However, less is known about for whom psychotherapeutic interventions for physical health conditions are effective. One reason for this might be pervasive underreporting of demographic data in research, despite the National Institute of Health's 2016 call to action to include such information. Specifically, studies that fail to report full demographic data of participants may reinforce inequities for historically and societally marginalized groups that are traditionally underrepresented in health research; function to restrict researchers from identifying nondiverse, unrepresentative samples; and limit the capacity for future research to address such limitations. To address this gap, we conducted a scoping review of reported demographic data in randomized clinical trials of psychotherapeutic interventions for cancer, obesity, and diabetes. We aimed to identify the frequency and type of demographic data in reported sample characteristics from 2016 to the present. Findings revealed that, on average, studies reported approximately 5 of the 8 demographic domains of interest (M = 5.1; SD = 1.24; range 3-7)-age, sex assigned at birth, race and ethnicity, sexual orientation, gender identity, marital status, education, mental health status-suggesting that researchers are not reporting demographic data regularly or consistently. The current article discusses the implications of underreporting demographic data for external validity and provides suggestions for future research directions. (PsycInfo Database Record (c) 2022 APA, all rights reserved).