The purpose of this study was to compare a national sample of gifted underachievers and gifted high achievers on a number of characteristics. Giftedness was measured as a composite score at or above the 95th percentile on the American College Testing Program (ACT). Underachievement was defined as reporting a high school grade-point average of less-than-or-equal-to 2.25 (on a 4.00 scale), and high achievement was defined as reporting a grade-point average of greater-than-or-equal-to 3.75 (on a 4.00 scale). Participants for this study were 30,604 high school juniors and seniors: gifted underachievers n=257: gifted high achievers n=30,347. The underachievers generally had lower scores on the ACT and less extensive out-of-class accomplishments. Over 90% of the underachievers were Caucasian males. Comparisons are provided on a number of nonacademic variables between underachievers and high achievers.