INTRODUCTION: Residual obstructive sleep apnea (OSA) after adenotonsillectomy (T&A) is a common problem in children with Down Syndrome (DS). Our objective was to describe trends in surgical and medical management of OSA in pediatric patients with DS, and to present an algorithmic approach to managing these children. METHODS: Retrospective case series of children with DS seen at a tertiary care medical center between 1/2008-6/2016 who underwent polysomnography (PSG) after having a T&A performed for sleep disordered breathing (SDB). RESULTS: Sixty-five patients met inclusion criteria. The mean age at T&A was 4.8 years and 52.0% were male. The mean apnea-hypopnea index (AHI) was 23.2 events/hour for patients who had pre-T&A PSGs. The mean AHI was 10.7 events/hour after T&A. Twenty-three patients (35.4%) underwent at least one additional surgical procedure after T&A; 5 (7.7%) patients had>/=two additional procedures. The most common additional surgical procedures were revision adenoidectomies (n=8) and lingual tonsillectomies (n=13). Fifteen (23.1%) patients underwent at least one drug-induced sleep endoscopy (DISE) to help direct selection of surgical site/s. CONCLUSIONS: Residual OSA is common after T&A in children with Down syndrome and can be managed by additional surgical interventions in many instances with successful reduction of the AHI. DISE has become part of a standard algorithm for managing persistent OSA in children with Down syndrome after T&A.