Lettuce aphid (Nasonovia ribisnigri) and western flower thrips (Frankliniella occidentalis)were tested together with iceberg lettuce from 20 cultivars for response to three day treatments of insecticidal controlled atmosphere with 5 and 10% CO2 and » 0% O2 at 5 and 10°C. All treatments resulted in complete control of insects. But the treatments also reduced visual quality and caused injuries by elevated CO2 and low O2. The higher CO2 level also coincided with more severe low O2 injuries to wrapper leaves and heart leaves. There were considerable variations in visual quality, CO2 injury, and low O2 injuries in response to controlled atmosphere treatments among lettuce cultivars. The results of cultivar variation in response to controlled atmosphere treatment suggest that we need to test many cultivars in developing controlled atmosphere treatments for postharvest insect control on iceberg lettuce.