21 cactus species occurring in various localities within Arizona were screened for the presence of fungal endophytes. 900 endophyte isolates belonging to 22 fungal species were isolated. Cylindropuntia fulgida had the maximum endophyte species diversity, while C. ramosissima harboured the maximum number of endophyte isolates. Alternaria sp., Aureobasidium pullulans, and Phoma spp. were isolated from several cactus species. The diversity of the endophyte assemblages was low and no host specificity among endophytes was observed. However, the frequencies of colonization of the few endophyte species recovered were high and comparable to those reported for tropical plant hosts. Species of Colletotrichum, Phomopsis, and Phyllosticta, which are commonly isolated as endophytes from plants of more mesic habitats, were absent from these cacti.