Mediterranean fruit fly,Ceratitis captitata(Wiedemann), was monitored with male lure trap collections and periodic collections of ripe fruits on the island of Kauai to determine its temporal appearance and distribution patterns. Results showed marked temporal differences in peak trap catches of the fly in lowland areas compared with upland areas. Flies were caught in two upland locations compared with catches in six lowland locations. Strawberry guava,Psidium cattleianumSabine, and common guava,Psidium guajavaL., form a discontinuous belt of plants around Kauai Infestation of this fruit byC. capitatawas nearly absent in wet areas and consistent but variable in dry areas. The seasonal appearance ofC. capitatain traps in Kokee and Polihale coincided with their emergence from collected fruits. The mean infestation rate ofC. capitatain guava was 0.43 ± 0.27 (mean ± SEM) per kg of fruit compared with 37.5 ± 15.3 forBactrocera dorsalis(Hendel), Infestation of all fruits collected byB. dorsaliswas widespread in all areas when these plants produced ripe fruits. Utilization of all fruits byC. capitatawas very limited in comparison with the distribution and abundance of host plants.