While CO2 is commonly used to anesthetize insects, it has been reported to have adverse effects on the biology of some species (Brooks 1965, Edwards and Patton 1965, Edwards 1968). Sherman (1953) found that CO2 anesthesia of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), resulted in increased mortality. Early experience at this laboratory also was that CO2 was detrimental to C. capitata , and as a consequence adults have always been manipulated without anesthesia. However, before a projected investigation of the effect of gamma radiation on adult C. capitata could commence, a means of immobilizing adults to facilitate handling had to be found. We therefore evaluated the effect of different periods of chilling, nitrogen anesthesia, and CO2 anesthesia on mortality, female fecundity, and egg hatch.