The Behavior Rating Inventory of Executive Function–Adult Version (BRIEF-A) is a standardized rating scale of subjective executive functioning. We provide univariate and multivariate base rates (BRs) for scale/index scores in the clinical range (T scores ≥65), reliable change, and inter-rater information not included in the Professional Manual. Participants were adults (ages = 18–90 years) from the BRIEF-A self-report (N = 1,050) and informant report (N = 1,200) standardization samples, as well as test–retest (n = 50 for self, n = 44 for informant) and inter-rater (n = 180) samples. Univariate BRs of elevated T scores were low (self-report = 3.3%–15.4%, informant report = 4.5%–16.3%). Multivariate BRs revealed the common occurrence of obtaining at least one elevated T-score across scales (self-report = 26.5%–37.3%, informant report = 22.7%–30.3%), whereas virtually none had elevated scores on all scales. Test–retest scores were highly correlated (self = .82–.94; informant = .91–.96). Inter-rater correlations ranged from .44 to .68. Significant (p < .05) test–retest T-score differences ranged from 7 to 12 for self-report, from 6 to 8 for informant report, and from 16 to 21 points for inter-rater T-score differences. Applications of these findings are discussed.