Abstract: An enclosure for electronic devices has a wall of a rigid plastic material, with elongated chambers defined therein. The chambers are filled with a material having a high thermal conductivity, or materials having high heat capacity, such as phase change material. Each chamber is located so that the material in the chamber is in thermal contact with the wall at a first location that tends to be at a relatively high temperature, and at a second location that tends to be at a lower temperature. The enclosure may alternatively have heat pipes of metal rather than chambers.