The continuous release of fission gas from ceramic fuels is measured during irradiation in the Oak Ridge Research Reactor. The fuel specimens are heated by their own fission power which is controlled by moving the specimen holder into or out of the neutron flux. Fuel specimens with thin cross sections are used, both to prevent thermal stress rupture and to allow accurate temperature measurement. A continuously flowing sweep gas carries the fission gas outside the reactor where the radioactive isotopes are measured with a gamma-ray spectrometer. The specimen temperature is controlled by air cooling the specimen holder. The experiment is instrumented to function continuously and unattended.