When a gas mixture containing carbon dioxide (CO2) is inhaled by an individual, alveolar ventilation is increased. This ventilatory response to CO2 highlights the relationship between the increase in exercise ventilation and the increase in alveolar CO2 pressure (paCO2). This response is mediated centrally by brainstem chemoreceptors in the medulla and, to a lesser extent, peripherally by the carotid and aortic bodies. However, the response of increased breathing to rising paCO2 varies markedly among individuals. The responses to CO2 rebreathing have been investigated by a variety of research groups for different reasons. The range of responses by children and adults including: gender differences; responses by athletes; the relationship between age and body size; and whether it is an acquired or inherited response have been studied. The following is a summary of these different aspects of CO2 rebreathing has been complied to assist researchers studying any single or multiple facets of the area.