Factors to be considered in planning and implementing a microcomputer local-area network (LAN) in a pharmacy department are discussed. Reasons for implementing a LAN include the ability to share data, programs, and peripheral devices among multiple users. The network operating system may be full featured or a peer-to-peer system. Full-featured networks require a dedicated file server but are more powerful and versatile. The file server, if used, is the most important piece of equipment. Factors that affect the choice of a file server are the processor, the bus, memory and speed, the supplier, and the power supply. It is necessary to select network adapters and wiring and to decide whether any of the department's current computer equipment will be used in the network. Decisions must also be made about software. The equipment should be set up by the computer services department or a vendor. Two or more pharmacists must be appointed and trained as supervisors to manage the network, diagnose and correct problems, perform network backup, and guard against computer viruses. Security is a major concern because of the need for confidentiality, the licensure of software for only a limited number of users, and the risk of inadvertent alteration or erasure of data. Network users must be trained to use the system properly. Department managers should consider the need to access the LAN from computers outside the department and the possible incorporation of the LAN into a wide-area network. A microcomputer LAN can provide valuable information services, but careful planning is necessary to avoid pitfalls and to ensure that the network meets current and future needs.