PurposeThe current study evaluates the demographic, clinical, and neurocognitive characteristics of a recruited FEP research sample, a research control group, and a FEP clinic sample that were assessed and treated within the same center and time period.MethodsThis study utilized data collected through an observational study and a retrospective chart review. Samples were ascertained in the Longitudinal Assessment and Monitoring of Clinical Status and Brain Function in Adolescents and Adults study and the Prevention and Recovery in Early Psychosis clinic. FEP clinic patients (n = 77), FEP research participants (n = 44), and age-matched controls (n = 38) were assessed using the MATRICS consensus cognitive battery and global functioning social and role scales. Between-group differences were assessed via one-way ANOVA and Chi-square analyses.ResultsNo significant differences were observed between groups with regard to age and gender. The FEP research sample had a higher proportion of white participants, better social and role functioning, and better neurocognitive performance when compared with the FEP clinical population. The clinic sample also had more diagnostic variability and higher prevalence of substance use disorders relative to the FEP research sample.ConclusionsResearchers should be aware of how study design and recruitment practices may impact the representativeness of samples, with particular concern for equal representation of racial minorities and patients with more severe illness. Studies should be designed to minimize burden to promote a wider range of participation.