SummaryIn April 1972, the (Belgian) Association for the Quality in clinical Biology has launched a proficiency testing program in the area of microbiology. At present 105 laboratories adhere to this program, and 88% of them participate actively at the different trials. The trials are organised at trimestrial intervals and each comprises the identification of three pure cultures and the determination of their susceptibility to 10 antibiotics. After each survey a detailed report is sent to the participants, giving the results of the identifications and the antibiotic susceptibility tests (performed according to Bauer-Kirby) together with a statistical and anonymous assessment of the overall performance of the participating laboratories. The report also contains recommendations on suitable identification techniques.The results of the 9 trials carried out during a period of 24 months, are represented in a series of tables. The choice of the cultures, submitted for identification, is briefly discussed. Important discrepancies in the results of susceptibility tests demonstrate the need for a standardised national reference technique and the necessity for regular inclusion of control-organisms with known sensitivity. In spite of certain criticisms and shortcomings, the program was wellcomed by most laboratories. Not only does it stimulate the emulation among laboratory technicians, but it also creates the need for a system of day-to-day quality control monitoring. Its didactic role has been highly appreciated. An expansion of the program to include clinical serology is now under way.