A computerized system called ARTEMIS has been taking part in the management of a referral hypertension clinic since September 1975. From January 1, 1976 to January 1, 1979, 3,624 patients' records were set up and updated, all of them accessible on line. The mean rate of response to 17 questions with obligatory answers concerning patients' past history was 97.6 per cent. The 10 routine laboratory tests included in the initial in-hospital work-up were registered in over 92 per 100 of the 2,651 hospital records examined. Negative responses were registered with the same accuracy as positive ones, when the computerized questionnaires were appropriately drafted. Standardized collection of information insured homogeneity of the medical staff and has already made possible epidemiologic studies. ARTEMIS has detected strategical errors such as the lack of yearly programmed tests for cardiovascular risk-factors associated with hypertension. The computer has helped to achieve a high rate of patient compliance at one year (81.3 per cent), by providing patients up-dated editions of their personal summary reports as well as sending periodical letters of recall to them and to their physicians. At a total annual cost of 11 dollars per patient, the computer provides continuous information on process and outcome, for each patient and physician, and for the entire population followed up at the clinic. It facilitates physician adherence to predefined protocols and reinforces follow-up continuity by creating a communications network between the referral clinic, the patient and the general practitioner.