The purpose of this study was twofold: (1) to determine the percentage of 6-18-year-old students who passed the FITNESSGRAM criterion scores for percent body fat (%BF), body mass index (BMI), mile run (MR), sit-ups (SU), pull-ups (PU), and sit and reach (S&R), and (2) to suggest and illustrate the instructed- uninstructedlmastery-nonmastery technique for the validation of criterion-referenced cut-off scores. The data base consisted of the NCYFSI and II national probability samples of students. Results shewed that the most frequently passed item was the S&R (M = 90%; F = 97%), followed by the two body composition items (%BF: M = 89%; F = 91%) (BMI: M = 88%; F = 85%), the MR (M = 77%; F = 60%), SU (M = 65%, F = 57%), and finally the PU (M = 73%; F = 32%). It is recommended that the criterion cut-off scores be statistically validated using the illustrated technique when the active (instructed) group has been trained with documented levels of frequency, intensity, and duration and the inactive (uninstructed) group is truly sedentary. © 1990 Taylor and Francis Group, LLC.