[en] A field experiment was conducted to assess the mating competitiveness of sterile males of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), in a natural population on Maui, HI. Systematic censuses of the study site were conducted before and after the release of marked sterile flies (both sexes), and the abundance and distribution of fruit flies and leks, incidence of male calling and number, and location of matings were recorded during the two periods. In both replicates, the abundance, distribution, and calling activity of wild males were largely unaffected by the released flies. Most of the released males joined preexisting mating aggregations of wild males and within these leks displayed similar calling activity as the wild males. Approximately 200 matings were observed following the release in each replicate. Three separate analyses indicated that in both replicates release males accounted for fewer matings with wild females than expected by chance. Given that sterile males settled and called in natural lek sites, it appears that their relatively low mating success resulted from an inability to attract wild females to their territory or perform courtship acceptable to females, or both. The results are discussed in light of current sterile insect techniques