Sheaff, AK, Bennett, A, Hanson, ED, Kim, Y-S, Hsu, J, Shim, JK, Edwards, ST, and Hurley, BF. Physiological determinants of the candidate physical ability test in firefighters. J Strength Cond Res 24(11): 3112-3122, 2010-The purpose of this study was to examine the relative importance of physiological characteristics during firefighting performance, as assessed by the Candidate Physical Ability Test (CPAT). Subjects included career and volunteer firefighters aged 18-39 (N = 33). Upper- and lower-body strength, muscle endurance, lower body muscle power, body composition analysis, aerobic capacity, anaerobic fitness, and the heart rate (HR) and blood pressure response to stair climbing were assessed to determine the physiological characteristics of the subjects. To quantify firefighting performance, the CPAT was administered by members of the fire service. Absolute and relative mean power during the Wingate anaerobic cycling test (WAnT), relative peak power during the WAnT, and absolute maximal oxygen uptake (JOURNAL/jscr/04.02/00124278-201011000-00030/ENTITY_OV0312/v/2017-07-20T235430Z/r/image-pngo2max) were significantly higher in those who passed the CPAT (N = 18), compared to those who failed (N = 15; p < 0.01). Mean power during the WAnT, fatigue index during WAnT, absolute JOURNAL/jscr/04.02/00124278-201011000-00030/ENTITY_OV0312/v/2017-07-20T235430Z/r/image-pngo2max, upper body strength, grip strength, and the HR response to stair climbing were significantly related to CPAT performance time (p < 0.01). Absolute JOURNAL/jscr/04.02/00124278-201011000-00030/ENTITY_OV0312/v/2017-07-20T235430Z/r/image-pngo2max and anaerobic fatigue resistance during WAnT best predicted CPAT performance (Adj. R2 = 0.817; p < 0.001). Performance on the ceiling breach and pull was the only CPAT task that was not significantly related to the physiological characteristics assessed. Measures of anaerobic and cardiovascular fitness best predict overall CPAT performance, and individual task performance. Remedial programs aimed at improving firefighting performance should target anaerobic and aerobic fitness qualities.