The frequent interruption of male courtship in highly crowded mass-rearing cages of Ceratitis capitata (Wiedemann) was correlated with changes in both male courtship and female acceptance criteria in a mass-reared Costa Rican strain, in accord with previous studies of other strains. Abbreviation of courtship behavior by mass-reared males was associated with the loss of the wild-type female tendency to reject males that performed shorter courtships. Consideration of probable costs and benefits of female choice in mass-rearing cages suggests that inadvertant selection in the cages probably favored the change in female criteria because females obtained sons with more effective courtship behavior.