['We sought to determine the frequency of progression in infants of perianal abscess with and without surgical drainage to fistula in ano to optimize a treatment plan for these children.', 'A retrospective cohort study was conducted of all patients who were < or = 1 year of age and presented with perianal abscess to 2 pediatric tertiary care institutions during a 10-year period (January 1995 to February 2005, inclusive). Patients were divided into those who underwent surgical drainage and those who did not, and the rate of subsequent fistula formation was determined.', 'Of 165 children initially identified, follow-up was available for 140. Ninety-four percent of children were male. Mean age was 4.2 +/- 3.1 months. Of the 140 patients, 83 abscesses were drained and 57 were not drained. Of patients who underwent surgical drainage, 50 developed a fistula, whereas of those who did not undergo drainage only 9 developed a fistula. Synchronous administration of antibiotics (intravenous or oral) used in 57 of 58 patients from 1 institution was associated with an even greater decrease in fistula formation (12.5%) in the undrained population.'] Is nonoperative management of perianal abscess in infants associated with decreased risk for fistula formation?