A 20 year old female from Compostela Valley Province in the Philippines, presenting with chronic diarrhea, borborygmi, bipedal edema, anorexia and weight loss was seen at Davao Regional Hospital. Her stool specimen, suspected by a local medical technologist to have Capillaria philippinensis ova, was forwarded to the Diagnostic Parasitology Laboratory of the College of Public Health, University of the Philippines Manila. It was examined and found to contain Capillaria philippinensis adults, larvae and eggs. Twelve deaths among people coming from the same barangay, affected by a similar illness with no definite diagnosis except "gastroenteritis" were also reported. These prompted health officials to send a team that would investigate the etiology of the disease outbreak labeled as a "Mystery Disease". Seventy-two stool samples from symptomatic patients were examined. Fifty-three (73.6%) individuals were proven to harbor at least one parasite with 16 (22.2%) individuals positive for Capillaria philippinensis infection. Ocular inspection, interviews and focus group discussions revealed that the people's eating habits are not much different from the habits of those from the Ilocos provinces where capillariasis was initially described. In both areas, people are fond of eating kinilaw or raw fish. They also eat raw shrimps, crabs and snails. Furthermore, the people defecate in the field or in the same body of water where they get the fishes, shrimps, crabs and snails that they eat, thus completing the life cycle of Capillaria philippinensis. Fish-eating birds were likely to have spread this parasite to the area. This is the first report of a capillariasis outbreak in Compostela Valley Province, and this should alert health authorities to consider embarking on serious efforts for developing proficiency of laboratory and clinical diagnosis especially in government health facilities where the poor and marginalized sectors of society are likely to consult.