The Munich Blood Pressure Program (MBP) is a community hypertension control program for the metropolitan area of Munich. It tries to improve "incidental screening" in doctors' offices in the city through continuing education programs for physicians and auxiliary personnel and, in addition, emphasizes worksite screening to bring high-risk hard-to-reach groups under treatment and control. Blood pressure (BP) is measured at the worksite under standardized conditions. Those with values greater than or equal to 140 mm Hg systolic BP and/or greater than or equal to 90 mm Hg diastolic BP at the first visit have BPs measured again within 1-5 days. If their BP values are still elevated, they are referred to their family physicians for further assessment. At the same time, they are given a postage-paid card on which their doctors are asked to note the BP value measured in their offices. This postcard is returned to the MBP for evaluation. A computer-based reminder system informs all MBP participants at certain time intervals to have their BP checked. The text of the letters and the time interval between them depend on the most recent BP and treatment status data available to the MBP. In 1983, screenings were performed in seven firms. Participation rates of up to 57% were achieved for this entirely voluntary examination (3,948 participants). Age- and sex-specific prevalence rates (for the pooled data of the seven firms) were similar to those of a random sample of the Munich population (Munich Blood Pressure Study I). Seventy-four percent of those with elevated BP at first visit participated in the remeasurement at a second visit. Only 58% of these showed elevated BP values the second time. More than half (n = 101) of those second-visit hypertensives (greater than or equal to 160/95 mm Hg; n = 183) returned at least one completed postcard. The examining physician confirmed the hypertensive BP values in 60 of those cases. Of the 101, 57 were under treatment, 19 controlled and 38 uncontrolled. The follow-up period considered here lasted until May 1984 and varied from 5 to 15 months according to the date of screening in the respective firm. Only the first returned card has been evaluated thus far.