Cardiac power output (CPO) is a descriptor of cardiac function, calculated from the product of mean arterial blood pressure and cardiac output. Previous studies (Bain et al. 1990) have suggested that maximum cardiac power output (CPO_peak) and the ability to increase cardiac power output on stimulation are good descriptors of functional cardiac reserve. The normal range for CPO_peak has yet to be determined and the purpose of this study is to establish this in healthy adults. The study also examined the relationship between CPO_peak and peak oxygen consumption rate (V_O2,peak) in the same population. After obtaining ethical approval and informed consent, 59 healthy adults (31 males and 28 females, means ± S.D.: age 43 ± 13 years, mass 74 ± 13 kg) completed an incremental exercise test to volitional fatigue using the protocol described by Bruce et al. (1973). V_O2,peak was assessed on a breath-by-breath basis by online expiratory gas analysis (CardiO₂, Medical Graphics Corp., St Paul, MN, USA). Having established each subject’s V_O2,peak, and following a 40 min recovery period, cardiac output was measured at peak exercise (Q_cpeak) using the non-invasive CO₂ rebreathing method described by Defares (1958). During this second procedure, subjects attained a mean oxygen consumption rate of 101 ± 7 % of the V_O2,peak achieved in the previous test. CPO_peak, in Watts (W), was then computed using the equation described by Cooke et al. (1998). Mean ± S.D. values for the variables investigated were: V_O2,peak = 2.47 ± 0.7 l min^-1, Q_Tpeak = 18.3 ± 4.5 l min^-1, and CPO_peak = 4.7 ± 1.3 W. The relationship between V_O2,peak and CPO_peak was assessed by the Pearson product moment correlation coefficient. Analysis revealed a strong (r = 0.91, P < 0.01) correlation between the two variables. CPO_peak ranged from 3.80 to 7.94 W in men and 2.53 to 5.57 W in women. Although the sample size remains moderate, the cardiac power output values attained were normally distributed and these values provide a useful indication of the normal range for CPO_peak in healthy adults.