This is a retrospective case series study describing 13 patients with biliary ascariasis treated between January 1989 to January 1995 in a tertiary regional training hospital. The mean age was 35 years (15-58 years). There were 10 females. All patients belonged to the low socio-economic class. Abdominal pain localized at the epigastric and/or upper quadrant area, characterized as moderate to severe, colicky and unrelenting, was present in all patients. Vomiting occurred in 11 patients (84.6%), and abdominal tenderness in 9 patients (69.2%). Jaundice was present in six cases (46.2%). Six out of 13 cases (46.2%) had normal temperature. In 10 cases (76.9%) the leukocyte count was higher than 10.0 x 10 . Ten patients underwent ultrasonography and 7 were correctly diagnosed as biliary ascariasis. Eleven patients succesfully underwent surgery with no operative mortality. In two patients, there appeared to be migration of the worms out of the biliary tree. One patient died of septicemia before surgery was performed. (Author)