Most of the parameters recorded in electrophysiology are strongly temperature dependent. In order to control temperature fluctuations we have built a system that ensures an accurate thermoregulation of the recording chamber. Temperature of physiological preparations can be changed relatively quickly (about 8°C/min) and with a good accuracy (±0.5°C) without inducing thermal oscillations. Contrary to other thermoregulating devices, the temperature regulation is not carried out through the perfused medium but directly at the bottom of the chamber where a 3-cm² Peltier element has been placed. The element is driven by a dedicated electronic device which controls the amount and the direction of the current flowing across the Peltier thermocouple. All construction details and the appropriate electrical circuits are provided. Using this home-made device, the steady-state chamber temperature could be precisely monitored with a resolution of ±0.1°C in a range of 0–40°C. This set-up was tested in experiments designed to evaluate the temperature dependence of synaptic transmission in the Torpedo nerve–electroplate synapses and of calcium currents recorded from isolated nerve cells. This low-cost method is suitable for a wide range of applications.