The purposes of this study were (a) to describe the relation of 1-mile run/walk time (MRWT) to skinfold thickness measures in a national probability sample of students 8 to 18 years of age (NCYFS I and II, n = 11,123) and (b) to evaluate the impact of adjusting MRWT scores for the effect of skinfold thickness on the classification of scores using percentile ranks and criterion referenced standards (CRS). MRWT was significantly related to the sum of subscapular and triceps skinfolds in all age-gender groups. In 12-year-olds, MRWT scores adjusted for sum of skinfolds by regression analysis resulted in individual percentile ranks that differed by more than 10 from percentile ranks of unadjusted scores in 29% of girls and 39% of boys, and altered classifications on the Fitnessgram and AAHPERD mile run/walk time CRS in 11-14% of boys and girls. It is concluded that the relation between MRWT and skinfold thickness is strong enough, and the impact of adjusting MRWT scores for skinfold thickness sufficient, to justify using adjusted scores for classification of cardiorespiratory capacity as part of the assessment of health related physical fitness in youth. Additional research is needed to cross-validate the equations developed in this study.