Computer-based pharmacy (PHARM) systems have notably improved thequality and safety of medical care. By the 1980s automated ward-based medication cabinets were available to support drug administration and pharmacy management, overcoming problems encountered when drugs were stocked in nursing stations, administered to patients at different hospital locations, and recorded in different paper-based records. When the growing use of prescribed drugs in patient care resulted in an increasing number of adverse drug events (ADEs), PHARM systems were used together with computer-based physician order entry/results reporting systems (CPOE/RRs) systems to prevent and detect such events. With greater computer storage capa-bilities and much larger databases, PHARM systems were better able to discover and monitor ADEs in inpatient and outpatient care for prescription drugs and over-the-counter medications. With links to comprehensive patient data within a defined popula-tion database, they could calculate rates of diseases and rates of ADEs. Medication reconciliation and interoperability standards such as RxNorm and Health Level 7 messaging supported sharing information across institutions. User-centered design focused on making systems more effective and reducing alert fatigue. Pharmacogenomics is expected to influence medication therapy and improve the safety and effectiveness of prescribed drugs; the interactions which occur in polypharmacy will lead to fewer medication complications in the elderly; and better understanding of pharmacokinetics will lead to improved dosing and timing of medications.