Mendez-Cornejo J, Gomez-Campos R, Andruske C, Sulla-Torres J, Urra-Albornoz C, Urzua-Alul L, Cossio-Bolanos M. Maximum Oxygen Consumption: Validity of the Run Test of 20 Meters and Proposal of Equations for Prediction in Young People. JEPonline 2020;23(1):24-37. 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 VO2 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-1) and relative (mL∙kg-1∙min-1) VO2 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 ± 9.8 L∙min-1, field X = 49.3 ± 9.8 L∙min-1) and relative (criterion X = 3.3 ± 0.8 mL∙kg-1∙min-1 field X = 3.4 ± 0.8 mL∙kg-1∙min-1). The coefficient of concordance index (CCI) varied from 0.89 to 0.95. Three equations were created for the absolute VO2 max: (R2 = 90 to 94%), and three other equations for the relative VO2 max: (R2 = 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 VO2 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.