Short-term storage regimens containing elevated atmospheres of carbon dioxide (CO₂) were evaluated for their ability to disinfest newly harvested ‘McIntosh’ apples of apple maggot, Rhagoletis pomonella (Walsh). Infested fruits containing newly laid eggs were either placed directly into the high-CO₂ atmosphere at 10°C to expose this life stage, or else held first for 7 d at room temperature, to allow development to the neonate larval stage. Treatment combinations consisted of three different CO₂ levels (10.6, 14.9, and 19.0% CO₂) and two periods of exposure (7 and 14 d). Apple maggot eggs subjected to the treatments always exhibited some survival, which was lower for the 14-d than the 7-d exposure periods. In contrast, newly hatched larvae were less able to survive the treatments. The 7-d exposure allowed low levels of survival of this life stage, but virtually none survived the 14-d exposure period. To determine the age at which eggs become more susceptible to high-CO₂ atmospheres, infested fruits containing eggs three or 5 d old were submitted to a 14-d exposure to 19.0% CO₂. Survival of 3-d old eggs was similar to that of eggs exposed at an age of 1 d or less, but this dropped to near zero for 5-d old eggs, indicating an increase in susceptibility sometime during the 3–5-d age range. Fruits exposed to 19.0% CO₂ for 14 d were significantly firmer than untreated fruits. No apparent browning, internal breakdown or other fruit defects were detected in any of the treatments.