Male–female interactions among three wild and three laboratory strains of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), were observed on caged trees in Hawaii and Guatemala. Sterile and wild males appeared comparable at attracting wild and sterile females into their territories and initiating courtship. Wild females, though, consistently accepted courtship overtures of wild males more readily (copulation occurred in 28% of 199 interactions) than they accepted those of sterile males (8% of 261 interactions). Depending on the strains involved, wild females were more likely to reject sterile (versus wild) males during the male’s courtship display, after the male mounted the female, or both. Sterile females accepted sterile males in 23.8% of 407 interactions and wild males in 26.1% of 257. Periodicity of mating behavior varied somewhat among strains, but sterile flies did not mate consistently earlier or later in the day than did wild flies. Less-than-desirable levels of mating compatibility between sterile and wild C. capitata appear to result primarily from the relatively low rates at which wild females accept courtship overtures of sterile males.