A distinct distribution pattern for the Mediterranean fruit fly,Ceratitis capitata(Wiedemann), on the island of Kauai, Hawaii, was determined from trap and fruit infestation data.C. capitatawas found at upper elevations as expected. However, it was also found breeding in low-elevation localities along the coast and in major valleys of western Kauai. Traps in areas that receive little rainfall consistently caught higher numbers ofC. capitatathan those in areas that receive abundant rainfall. Hosts were generally abundant in ecotone areas between dry and wet habitats. The most important hosts were coffee,Coffea arabicaL., strawberry guava,Psidium cattleianumSabine, and peach,Prunus persica(L.) Batsch. There was evidence thatC. capitatamoved from these areas into certain dry areas. Generally, populations ofC. capitatawere absent from large areas of native forests except where the alien strawberry guava had invaded. Our study differed from previous studies by its heavy reliance on plastic fruit fly traps for delineating distributional limits ofC. capitataover large and remote areas. Once flies were detected in an area, host fruit collection data were used to establish whether flies were breeding in an area.