The ISO 9001 quality assurance of the National Institute of Oncology has been achieved successfully. We give an account of the brief history and the structure of the assurance system of the Institute, the process of setting our goals, and also the experience gained from drafting ISO 9001 handbook and flowcharts. Apart from the bureaucratic nature of quality assurance, it is a good opportunity for us to investigate our everyday work, put it into orderly manner and work more reliably. Experience has shown that the introduction of a quality assurance system increases the level of patient care, the documentation helps the Institute or some of its departments, or even individuals prevent law suits, and serves as a sound basis for proposing promotion, salary increases and bonuses, or even honors.