The purpose of this investigation was to determine the validity of the non–exercise-based equations of Davis et al. (13), Jones et al. (20), and Neder et al. (30) for estimating the ventilatory threshold (VT) in samples of aerobically trained men and women. One hundred and forty-four aerobically trained men (mean ± SD age, 41.0 ± 11.6 years; N = 83) and women (37.1 ± 9.0 years, N = 61) performed a maximal incremental test to determine JOURNAL/jscr/04.02/00124278-200702000-00006/ENTITY_OV0312/v/2017-07-20T235329Z/r/image-pngO2max and observed VT on a cycle ergometer. The observed VT was determined by gas exchange measurements using the V-slope method (JOURNAL/jscr/04.02/00124278-200702000-00006/ENTITY_OV0312/v/2017-07-20T235329Z/r/image-pngCO2/JOURNAL/jscr/04.02/00124278-200702000-00006/ENTITY_OV0312/v/2017-07-20T235329Z/r/image-pngO2) in conjunction with analyses of the ventilatory equivalents (i.e., minute ventilation JOURNAL/jscr/04.02/00124278-200702000-00006/ENTITY_OV0312/v/2017-07-20T235329Z/r/image-pngE/JOURNAL/jscr/04.02/00124278-200702000-00006/ENTITY_OV0312/v/2017-07-20T235329Z/r/image-pngO2 and JOURNAL/jscr/04.02/00124278-200702000-00006/ENTITY_OV0312/v/2017-07-20T235329Z/r/image-pngE/JOURNAL/jscr/04.02/00124278-200702000-00006/ENTITY_OV0312/v/2017-07-20T235329Z/r/image-pngCO2) and end-tidal gas tensions (i.e., PETO2 and PETCO2) for oxygen and carbon dioxide. The predicted VT values from 14 equations were compared to the observed VT values by examining the constant error (CE), standard error of estimate (SEE), Pearson correlation coefficient (r), and total error (TE). The results of this investigation indicated that all 14 equations resulted in significant (p < 0.008) CE values ranging from 1.13 to 1.72 L·min−1 for the men and from 0.58 to 1.12 L·min−1 for the women. Furthermore, the SEE, r, and TE values ranged from 0.37 to 0.54, from 0.36 to 0.53, and from 0.68 to 1.81 L·min−1, respectively. The lowest TE values for the men and women represented 45 and 36% of the mean of the observed VT values, respectively. The results of this study indicated that the errors associated with all 14 equations were too large to be of practical value for estimating VT in aerobically trained men and women.