Intraoperative temperature regimen is usually planned preoperatively ‘in team’. Selecting and understanding the impact of the temperature regimen (normothermia, or mild, moderate or severe hypothermia) is usually related to the type of cardiac surgery (e.g. using circulatory arrest or open-heart surgery). Cardiopulmonary bypass constitutes a challenging situation for monitoring temperature because of the rapid and extraordinary degree of heat transferred through the bypass circuit during heating and cooling. The core compartment undergoes the fastest temperature changes because of the rapid rate of blood reinfused into the organs. In modern cardiac surgery, different types and technologies of heater–cooler devices can be used in clinical practice, thanks to the development process that took its cue from past experiences. In this context, we review the role of thermal exchange in cardiac surgery and the progress achieved from first- to second-generation heater–cooler devices.