Experiences in a two years application of electronic data processing in medical routine microbiology are reported. Optical mark reader forms serve as request forms as well as workprotocol. On the left two thirds of these forms (Fig. 1 and 2) the patients data including clinical statements, and the kind of specimen to be investigated (sputum, smear etc.) as well as results not essential for the printout of laboratory reports are filled in. On the right third of the optical mark reader form, in which area the Bell & Howell document reader can read pencil marks, the patients identification number, the tests requested and all results are marked right at the work bench. As shown in the flow diagram (Fig. 3) after completion of the investigation the date on the mark reader forms are read mechanically and the test results are printed (Fig. 5) by means of the computer. In addition, the data processing system, which proved to be very flexible, performs all necessary types of administrative work as filing of laboratory data in a coded form on cards for permanent storage (Fig. 7) statistics and the printout of bills (Fig. 6). The processing of routine microbiology date is achieved by a Siemens DVA 404/3 (64 kbt) connected for magnetic disc device (2993 Mio bytes), and a line printer (60,000 lines per hour) and dialog display monitors, which are used simultaneously for the on line and off line handling of all the data in clinical chemistry-, serology- and hematology-departments of the same institute.