The slowly increasing use of computers in the management of general medical practices may be greatly accelerated if new technologies for the storage and transfer of information are introduced. Electronic data interchange promises to speed the transfer of medical data, insurance information and payments. Smart cards promise a portable, up-to-date, confidential medical record that can be carried by patients. However attractive these new systems may be to computer suppliers and government bureaucracies, it is not certain that they will be as attractive for the general practitioners who will be required to implement the changes. Smart cards may exacerbate problems with the ownership and privacy of data, rather than guaranteeing confidentiality and control. Data exchange through a computer network may allow many information services not actually essential to general practice, while creating serious new possibilities for breaches of privacy. Costs in implementing the new technologies for general practices may outweigh any gains in efficiency, which could in any case be achieved through better use of paper records. The Health Insurance Commission may see advantages in the collection of data on the diagnoses of patients that can be used in epidemiological studies and in the control of overservicing, but there will be practical limitations on the reliability of the data collected by this means. General practitioners should carefully consider their attitude to these new technologies before suppliers, governments and others make their record-keeping decisions for them.