Cyclospora is a parasite traditionally associated with diarrhea in travelers to endemic countries. Recently, several cases of cyclosporiasis were reported in nontravelers in the United States and Canada, implicating various fruits and vegetables as vehicles of infection. The life cycle of cyclospora is not fully known, but is believed to involve both asexual and sexual stages of proliferation. Food- and water-borne transmission of infection have been implicated. Patients infected with Cyclospora cayetanensis have protracted watery diarrhea. Various generalized symptoms are also present, making cyclosporiasis indistinguishable from infectious diarrhea caused by other microorganisms. Diagnosis depends on identifying the organism by microbiologic examination of stool samples. Treatment consists of supportive care, maintenance of fluid and electrolyte status, symptomatic relief, and antibiotic therapy. Trimethoprim-sulfamethoxazole is the only antibiotic available that is effective in eradicating the organism.