['The purpose of this study was to follow the natural course of spontaneous passage (SP) of ingested foreign bodies (FBs) in children.', 'The medical records of 249 patients who ingested FBs were reviewed. In addition, they were studied by telephone questionnaires to follow up spontaneously passed FB. The factors associated with SP such as age, the type, size, and initial location of the FBs were analyzed.', 'Foreign bodies were spontaneously passed in 145 patients (58.2%), endoscopic removal was performed in 100 patients (40.2%), and operative removal was performed in 4 patients (1.6%). Most SP FBs were passed within 5 days. The SP rates (SPRs) according to the initial location were the following: 12.2% for the esophagus (P<0.0001), 71.4% for the stomach, 85.7% for the small bowel, and 96.4% for the colon. There was no significant difference in the SPR according to age. When coins and disk batteries that required early endoscopic removal were excluded, the SPR was 63.4% for FBs less than 10 mm, 80.4% for FBs 10 to 20 mm, 72.8% for FBs 20 to 30 mm, and 50.0% for FBs more than 30 mm (P=0.091). The initial location of the FB (odds ratio, 33.7; 95% confidence interval, 14.4-79.0) and the size of the FB (odds ratio, 3.5; 95% confidence interval, 1.0-11.6) were independent predictors of SP by multivariate analysis.'] Does initial location determine spontaneous passage of foreign bodies from the gastrointestinal tract in children?