Twenty-four college-age participants took part in 2 protocols on an aquatic treadmill (ATM) submerged to the xiphoid process. ATM speed was increased to 212.2 + 19.2 m/min, and water-jet resistance was increased 10% every minute thereafter. Rest between sessions was at least 6 days. Oxygen consumption (VO2), heart rate (HR), minute ventilation (VE), tidal volume (VT), breathing frequency (f), and respiratory exchange ratio (RER) were measured continuously. Rating of Perceived Exertion (RPE) was recorded immediately after each test, and blood lactate (LA) was measured 3 min after. There were no significant differences for Trial 1 vs. Trial 2 for any variable. ICCs were very strong (r = .90-.99) and coefficients of variants (CVs) were low (1.3-4.7%) for VO2peak, HR, VE, VT; ICC’s were moderate (r = .73-.76) and CVs were greater (2.5-9.3%) was greater for f, RER and LA. The ATM VO2peak protocol used in this study produces consistent, reproducible VO2peak values.