Over the last decade increasing numbers of enteritis cases have been attributed to infection with a new coccidian species that was named Cyclospora cayetanensis in 1993. Diarrhea caused by this agent is clinically indistinguishable from cryptosporidiosis, isosporiasis and microsporidiosis, but Cyclospora infections are often very prolonged (up to 15 weeks) and may cause severe weight loss. Diagnosis of infection is important because, in contrast to diarrhea caused by Cryptosporidium and microsporidia, treatment with co-trimoxazole is effective. Here we report the cases of two female patients, aged 70 and 58 years old, respectively, who suffered from severe, prolonged diarrhea after a vacation in Singapore, Java and Bali. Routine microbiological laboratory diagnostics were unable to demonstrate the presence of known enteropathogenic bacteria. Modified Ziehl-Neelsen staining of fecal smears revealed oocysts of Cyclospora cayetanensis, and treatment of the patients with co-trimoxazole was promptly effective. We would like to increase awareness of the possibility of Cyclospora infections in patients with prolonged diarrhea who have travelled to endemic areas.