Morphine Tonsilectomy and Adenoidectomy (T&A) Pharmacokinetics (PK) study will be done as a part of the larger institutional Center for Applied Genomics (CAG) project entitled "A Study of the Genetic Causes of Complex Pediatric Disorders" (GCPD study), as approved by the Children's Hospital of Philadelphia (CHOP) IRB, 2006-7-4886. By combining Genome Wide Association (GWA) and PK data, we wish to conduct a Pharmacogenomic (PG) study of IV morphine administered as standard of care during and after pediatric day surgery T&A. Because we expect several genes to play a role in the morphine response, we must use a large, relatively uniform pediatric surgical population such that for T&A. Through observation and minimal-risk blood sampling of this cohort of children, we hope to identify genetic variants that predict analgesic response to (and serum levels of) morphine sulfate. Pediatric patients ages 4-18 y, presenting with significant tonsillar/adenoidal tissue hypertrophy, sleep disordered breathing and/or recurrent infection, and requiring T&A are eligible. Morphine is the most common IV analgesic used for T&A at CHOP. As is necessary for accurately defining analgesic response phenotype, morphine will be administered in a structured manner consistent with standard of care at this institution. As defined below, children resistant to morphine (MR) and those sensitive to it (MS) will be identified as specific phenotypes to be compared with normal responders (NR) in a GWA study.