The syndrome of chronic heart failure (CHF) becomes increasingly prevalent in older patients, and while mortality rates are declining in most cardiovascular diseases, both prevalence and mortality in CHF remain high. The heart is unable to meet the demands of the skeletal musculature, and symptoms manifest as dyspnoea and signs of fatigue during exercise. The cardiopulmonary exercise test (CPET) can provoke symptoms which may be useful in improving the accuracy of diagnosis in CHF in a non-invasive setting. CPET also provides important information on the pathophysiology of exercise limitation, risk stratification and can establish exercise-training protocols. The information provided by the CPET allows suitable pharmacological or device-based adjustments to be considered in the management of CHF, which can be crucial in maintaining a patient’s quality of life. This manuscript provides a useful insight into the theoretical rationale and practical recommendations for CPET in patients with CHF. Prior to CPET, it is important to consider the mode of exercise, as cycle ergometry or treadmill protocols will yield different outcomes in patients with CHF. We discuss how pre-CPET set-up procedures should be conducted and also the significance of electrocardiographic abnormalities found in CHF patients, and how these should be interpreted. The assessment of lung function is integral to the underlying pathophysiological basis of exercise limitation and we explain how this should be performed. CHF patients display the following abnormal exercise responses which can be identified by CPET: peak oxygen uptake ( \( \mathop {\text{V}}\limits^{\text{.}}{\text{O}}_{\text{2}} \) peak), anaerobic threshold (AT), ΔVO₂/Δ work rate (WR), peak oxygen pulse, estimated peak stroke volume and predicted peak heart rate are reduced. The \( \mathop {\text{V}}\limits^{\text{.}}{\text{E/}}\mathop {\text{V}}\limits^{\text{.}} {\text{CO}}_2 \) slope is abnormally high and the breathing reserve is normal or high. An immediate post-exercise increase in O₂ pulse is evident, and/or a regular oscillatory breathing pattern has been observed at lower exercise intensities in some CHF patients. Symptoms of breathlessness, fatigue, and/or leg pain occur earlier during CPET and may cause the CPET to be aborted early. We explain the significance of the 9-panelled array, and how it can help to determine the underlying pathophysiology of exercise intolerance in these patients.