In the last few years the basis for national guidelines for the indications of coronary angiography, coronary revascularisation and hysterectomy has been established. The guidelines have been published and are accessible to medical doctors and patients on the Internet using a database system called "Second Opinion System": http:/(/)sos.inf.ethz.ch Dissemination, implementation and validation of the guidelines will be of major importance in the near future. With reference to validation, the question remains whether the established guidelines are correct for the everyday treatment of patients. A suitable method of answering this important question is comparison between the appropriateness and necessity rates of the various indication groups, combined with outcome measurements. The Internet-based second opinion system (SOS) may be used for data collection in order to verify hypotheses. Because of the database architecture, only relevant information about the patients is collected via Internet, independent of time and place. In addition, the system allows users to evaluate their individual data, and special attention is given to data protection. The discussion about priorities in health care (rationing) will be increasingly important in the near future. The present project may offer a way of maintaining adequate access to health care services for patients. Therefore, the participation of as many institutions as possible in the project "quality assurance of indication and outcome in interventional cardiology and in gynaecology" is of great importance.