The primary outcome will be medication reconciliation errors with a potential for causing harm (potential ADEs). Secondary outcomes will include the different types of reconciliation errors, hospital length of stay, emergency department visits and hospital readmissions within 30 days of discharge, resident/nurse satisfaction, and compliance with the reconciliation process. To measure medication reconciliation errors, we will use a method similar to that suggested by the Massachusetts Coalition for the Prevention of Medical Errors. A study pharmacist, separate from the floor pharmacist, will determine each patient's preadmission medication regimen at the time of hospital discharge, using patient and family interviews and any additional information needed to validate the list. This list will then be compared with the preadmission medication list compiled by the intern to identify any errors in identifying preadmission medications. The list will also be compared with the admission and discharge medication orders in order to identify unexplained discrepancies. Questions will be resolved by communication between the study pharmacist and the ordering intern. Reports of all potential medication reconciliation errors will be presented in blinded fashion to two physician reviewers, who will judge whether a reconciliation error has taken place and its potential for harm. All medication reconciliation errors will be recorded, as well as each of the individual types: inaccuracies in the preadmission medication list, unexplained discrepancies with the admission medication orders, and unexplained discrepancies in the discharge orders. This methodology is similar to that used in other studies of medication errors conducted at BWH. This process will allow pharmacists to ethically report any problems to the medical team prior to discharge, while still allowing for a full measurement of medical errors. Hospital length of stay, emergency department visits, and hospital readmissions will be measured using hospital administrative data. Resident and nurse satisfaction and perceived quality of patient care will be measured using web-based surveys. Compliance with the reconciliation process will be measured by electronic tracking of the use and timing of: 1) PAML building and signing by the ordering intern, 2) reconciliation of all PAML medications within 24 hours of admission, and 3) reconciliation of the PAML and discharge medication orders by the ordering clinician at the time of discharge.