Rates of ground radon emanation, in the Puna geothermal area on the lower east rift of Kilauea volcano, were measured by alpha particle sensitive cellulose nitrate films. The survey successfully defined an area of thermal significance associated with the rift structure, and suggests that a thermally driven ground gas convection system exists within, and peripheral to, the rift. This type of survey was found suitable for the basaltic island environmnet characteristic of Hawaii and is now used in Hawaii as a routine geothermal exploration technique.