A 1-year, randomized study was conducted to test the possibility of improving compliance with therapeutic regimens in hypertensives by means of certain simple arrangements. Patients were given written treatment instructions concerning hypertension, a personal blood-pressure follow-up card, and, for those who failed to attend their blood-pressure check-up, an invitation for a new check-up. Using matched pairs, 202 Finnish hypertensives were randomly allocated either to an ordinary or a reorganized treatment group. By means of the latter system, patient compliance could be significantly (p less than 0.01) improved: Only 4% of the patients in this group dropped out of treatment, compared with 19% in the ordinary treatment group. By the end of the year, blood pressure had been lowered by at least 10% in 95% of the patients in the reorganized group and in 78% of those in the ordinary group (p less than 0.01). This was achieved in approximately 60% of cases using chlorthalidone alone.