The purpose of this study was to assess the validity of a self-administered 3-day physical activity recall instrument (3DR) in young adults. Thirty-nine participants (age: 21.0+2.2 years; body mass index: 23.3+3.3 kg/m) wore an accelerometer during all waking hours for seven consecutive days and completed the 3DR on the eight day. During the 3-day recall period, participants accumulated 283,488.1+86,792.3 counts/day, 347.0+102.5 counts/minute, and reported spending 23.3 (IQR=35.0) and 11.7 (IQR=43.3) minutes in moderate and vigorous intensity activity, respectively. Counts/day and counts/minute correlated with self-reported minutes of vigorous activity (r=0.40, =0.01 for both variables). Results indicate that the validity indices of the vigorous 3DR items are similar to other self-report physical activity questionnaires. Health education and promotion professionals should consider using the 3DR when evaluating physical activity interventions in college students and young adults.