The purpose of this study was: (a) to verify the validity of a 20 m round trip run test for young athletes; and (b) to propose regression equations for predicting V[O.sub.2] max in young athletes. The sample for this study consisted of 31 young university students. Age ranged from 18 to 24 yrs old. The absolute (L*[min.sup.- (1])) and relative (mL*[kg.sup.-1]*[min.sup.- (1])) V[O.sub.2] max values were measured with a test in the laboratory and in the field (20 m round trip run test). Weight, standing height, body fat percentage (BF%), fat mass (FM), lean mass (LM), and maximum expiratory flow (MEF) were also measured. No differences were found between the laboratory and the field run tests in absolute terms (criterion X = 49.3 [+ or -] 9.8 L*[min.sup.- (1]), field X = 49.3 [+ or -] 9.8 L*[min.sup.- (1])) and relative (criterion X = 3.3 [+ or -] 0.8 mL*[kg.sup.- (1]*[)min.sup.- (1]) field X = 3.4 [+ or -] 0.8 mL*[kg.sup.- (1][)min.sup.- (1])). The coefficient of concordance index (CCI) varied from 0.89 to 0.95. Three equations were created for the absolute V[O.sub.2] max: ([R.sup. (2]) = 90 to 94%), and three other equations for the relative V[O.sub.2] max: ([R.sup. (2]) = 73 to 76%). The six equations demonstrated high values for Desirable Reproducibility Indexes (DRI) (precision 0.85 to 0.97) and (accuracy 0.94 to 0.99). The 20 m Back and Forth Run Test is valid for estimating absolute and relative V[O.sub.2] max in young athletes. Furthermore, the six equations developed for both sexes provide a reasonable alternative for evaluating aerobic fitness in the health and sport sciences context.