OBJECTIVE To compare the postoperative course and complications after tonsillectomy or tonsillectomy and adenoidectomy in children with Down syndrome (group 1) with the postoperative course and complications in children in a control group (group 2). METHODS Retrospective review of medical records for the period January 1, 1986, through March 30, 1996. METHODS Tertiary care children's hospital. METHODS The study included 87 children in group 1 and 64 children in group 2 matched for age, sex, and year of surgery. METHODS Tonsillectomy and adenoidectomy (group 1, 79 children; group 2, 57 children) and tonsillectomy (group 1, 8 children; group 2, 7 children). METHODS Length of hospitalization and postoperative complications. RESULTS The length of hospitalization was significantly increased for the children in group 1 compared with that of children in group 2 (1.6 vs 0.80 days; P=.001, Mann-Whitney U test). Twenty-two children (25%) in group 1 required airway management or observation in the pediatric intensive care unit compared with no children in group 2 who required such care (P<.001, Fisher exact test). None of the children in either group required reintubation, continuous positive airway pressure, or tracheotomy. Respiratory complications requiring intervention were 5 times more likely in group 1 (22 [25%] vs 3 [5%]; P<.001, Fisher exact test). The median time until intake of clear liquids and duration of intravenous therapy were significantly increased in group 1 compared with group 2 (5.0 vs 4.0 hours, P=.03; 23.5 vs 16.0 hours, P=.001, respectively; Mann-Whitney U test). CONCLUSIONS Although tonsillectomy and adenoidectomy can be performed safely in children with Down syndrome, the rate of postoperative respiratory complications is higher and the duration until adequate oral intake is resumed is longer. We therefore recommend that children with Down syndrome be admitted to the hospital overnight after undergoing tonsillectomy and adenoidectomy.