This study begins with a retrospective electronic database query of 2000 day surgery T&A cases between 11/1/2005 and 10/31/2008 in which morphine was used as the sole IV analgesic. Data from this portion of the study will help us refine phenotype parameters, should robust subpopulations of response types emerge, and provide background information required for eventual project funding by the National Institutes of Health (NIH). The prospective portion of the study will follow an additional 1650 children newly enrolled in the CAG study and now presenting for T&A.