It is becoming increasingly common for health care providers to present information on the World Wide Web (WWW).Patients, as wellas health care professionals, do not really know what they can expect today. Many quality criteria are proposed for the assessment of medical Internet sites focusing mainly on structure and content management. The objective of this study was to assess the quality of presentations by health care providers on the WWW and to detect strengths and weaknesses with regard to potential target groups, patients, colleagues, and students. A sample of 171 presentations was randomly selected in March 2000 from a collection of 469 surgical departments in Germany. Medical doctors undergoing a full-time training in medical informatics rated the presentations. A previously evaluated questionnaire was used to assess the presentations with regard to 12 criteria about content and technical features. For each criterion the categories 'very good', 'sufficient', and 'insufficient' could be used. Twenty medical doctors assessed 168 presentations with one to seven valuations per presentation. Three presentations could not be accessed at the time of evaluation. Sixty-eight per cent of the median values of each criterion were rated as insufficient. The only criteria rated sufficient or better in at least 50% were: employees/map, survey of offered medical services, navigation, and layout. University hospitals and heart centres achieved significantly better results than regional hospitals. In conclusion, the quality of provider information on the WWW is unsatisfactory. Most surgical departments do not provide information that could help patients to choose their physicians. The criteria set developed here could be a useful tool for a target-group-oriented self-assessment of provider presentations on the World Wide Web.