The purpose of this study was to develop and cross-validate a generalized equation for predicting &OV0312;O2peakfrom 1-mile run/walk (MRW) time and demographic variables in youth and young adults. Data for 753 males and females 8–25 yr of age were divided into validation (N= 495) and cross-validation (N= 258) samples. The validation sample was used lo develop a multiple regression equation for predicting treadmill &OV0312;O2peak(ml·kg−1min−1) from gender (0 = F, 1 = M), age (yr), body mass index (kg·m−1; BMI) and MRW time (min). The multiple correlation (R) and standard error of estimate (SEE) were: R = 0.71, SEE = 4.8 ml·kg−1·min−1. The accuracy of this equation was confirmed when applied to the cross-validation sample. The regression equation for the total sample was: &OV0312;O2peak= −8.41 (MRW) + 0.34 (MRW)2+ 0.21 (Age × Gender) −0.84 (BMI) + 108.94, R = 0.72, SEE = 4.8 ml·kg−1·min−1. We conclude that the generalized equation provides valid estimates of &OV0312;O2peakin youth and young adults. The equation should be useful for educators, clinicians, and researchers who would like to interpret results of the MRW test in terms of &OV0312;O2peak.