Objective: Report the distribution of scores from the Adult ADHD Self-Report Scale (ASRS) and estimate the prevalence of self-reported attention-deficit/hyperactivity disorder (ADHD) symptoms as compared to clinical diagnoses. Participants: Participants were 1,080 college students, divided into 3 groups: (1) no ADHD diagnosis (n = 972), (2) diagnosed with ADHD but no current pharmacologic treatment (n = 54), and (3) diagnosed with ADHD with current pharmacologic treatment (n = 54). Methods: The ASRS was administered during the fourth annual interview of an ongoing longitudinal cohort study. Results: As expected, individuals who were never clinically diagnosed with ADHD had lower ASRS scores (M = 4.0, SD = 3.3) than individuals diagnosed with ADHD who were either under current pharmacologic treatment (M = 7.9, SD = 4.0) or not under treatment (M = 6.3, SD = 3.7). Overall, 10.3%[subscript wt] of individuals without an existing clinical diagnosis of ADHD had high levels of ADHD symptoms. Conclusions: A substantial minority of undiagnosed individuals may benefit from a clinical assessment for ADHD. (Contains 1 figure.)