The overall objective of this study is to evaluate the impact on physician prescribing and subsequent patient outcomes of conducting pharmacokinetics analyses of blood samples from pediatric epileptic outpatients receiving selected anticonvulsant medications. Within the last decade, a new health discipline called Clinical Pharmacokinetics has emerged to assist clinicians in the therapeutic decision making process. Numerous Clinical Pharmacokinetic Laboratories (CPLs) have been established to provide analytical and consultative services to health care practitioners in hospitals, clinics and nursing homes. In order to assess the impact of CPLs, a retrospective study will be conducted to answer two research questions: 1) what is the impact of providing pharmacokinetic information on both physician prescribing and patient outcomes, and 2) what is the impact on patient outcomes of physician using that information in their decisions regarding drug therapy. Pediatric patients seen at the Exceptional Child Clinic (ECC) in the University of Maryland and Hospital will serve as the study population. Data on approximately 720 patients will be collected during the study Data will be collected concerning: 1) patient outcomes, such as the number and type of seizures, number of rehospitalizations, and number of toxic reactions, and 2) physician prescribing, such as drug name, dosage from strength and length of therapy. Data will be collected for two time periods: twelve months prior to the initiation of CPL services and twenty-four months following the initiation of services. Two separate analyses will be performed to test two hypotheses. In addition, a post hoc analysis of potential cost savings and expenses generated as a result of providing CPL information will be performed. The major significance of this proposal is that it will measure the impact of a non-threatening, relatively inexpensive intervention designed to maximize the quality and economy of physician prescribing.