In each of three field releases, a higher percentage of large, mass-reared, sterile Mediterranean fruit flies,Ceratitis capitata, was recaptured than either medium-sized or small flies, with large flies tending to be caught over a longer time period than small flies. Larger flies had a higher emergence rate and percent flight ability. Also, larger flies were significantly longer lived than smaller flies when deprived of food and water in laboratory quality control tests.