A detailed chronology of unsuccessful efforts to diagnose and treat a sudden-onset case of chronic diarrhea acquired in Jakarta Indonesia, and ultimately attributed to Cyclospora is presented. A modified Kato technique was used to quantify Cyclospora oocysts during successive days prior to, during, and after successful cotrimoxazole therapy (160 mg of trimethoprim, 800 mg sulfamethoxazole twice a day for seven days) for this infection. Cyclospora was associated with 6.4% of the gastrointestinal illness and/or diarrhea cases that presented during a seven-month period to a Jakarta clinic that serves a small population of expatriates. Cyclospora and Giardia lamblia were identified with equal frequency during this period and were the dominant pathogenic intestinal parasite species found in this community.