New technologies are now emerging that have Objective-To study the effects of the introduction considerable potential for improving communication.of electronic data interchange between primary and One such technology is electronic data interchange, secondary care providers on speed of communi-defined as "standard electronic messages conveyed cation, efficiency of data handling, and satisfaction from one computer to another without mdnual interof general practitioners with communication.vention. "' In the Netherlands several organisations Design-Comparison of traditional paper based have cooperated to standardise messages in health care communication for laboratory reports and admis-using the Edifact standard,"'''" which describes the sion-discharge reports between hospital and general syntax of messages. Several standardised messages practitioners and electronic data interchange.are available, including a laboratory report and an Setting-Twenty-seven general practitioners admission-discharge report. Using such a standardised whose offices were equipped with a practice infor-message a laboratory can, for instance, transmit test mation system and two general hospitals.results electronically to a general practitioner's comOutcome measures-Paper based communication puter system, which can then manipulate and store was evaluated by questionnaire responses from and the data automatically. interviews with care providers; electronic communiIn the Netherlands the infrastructure required for cation was evaluated by measuring time intervals electronic data interchange is emerging. Many hospitals between generation and delivery of messages and by have already had years of experience with information assessing doctors' satisfaction with electronic data systems, and in primarv care computer based patient interchange by questionnaire.records are gaining ground rapidly. At present half of Results-Via paper mail admission-discharge all Dutch general practitioners (over 3000) are using an reports took a median of 2-4 days, and laboratory information system in daily practice, and 1300 of them reports 2 days, to reach general practitioners. With are using computer based patient records. electronic data interchange almost all admissionIn this paper we describe a project that studied discharge reports were available to general prac-electronic communication between hospitals and titioners within one hour of generation. When general practioners. The aims of the study were (a) to samples were analysed on the day of collection (as introduce electronic data interchange in a health care was the case for 174/542 samples in one hospital and environment, (b) to assess the gain in speed of delivery 443/854 in the other) the laboratory reports were of reports achieved using electronic data interchange Department ofMedical also available to the general practitioner the same instead of paper mail, (c) to measure the influence of