Germany's health care system is based on statutory health insurance funds and the legal obligation of those physicians who work on a contractual basis with the health insurance companies to guarantee the outpatient medical care of the insured. Despite the widely acknowledged efficiency of this system it fails to have the desired effect on those sections of the population who cannot enforce their claims for help or who do not meet the requirements of institutional working conditions. Mostly concerned are homeless people with an additional drug problem or mental disease, immigrants as well as children from socially disadvantaged families. Their number increases especially in the big cities, but legal and organisational limitations render the necessary and time-consuming support impossible, which requires to call on and follow up on patients. The city of Cologne has temporarily established a mobile medical service at the public health department for the subsidiary care of the people concerned. The medical team treats its patients--unbureaucratically and without prerequisites on the part of the patients--in a mobile ambulance or in facilities of social institutions, which take care of drug addicts and homeless people. The physicians who work on a contractual basis with the health insurance companies cooperate with this service to take on this social-compensatory common task. The health insurance companies do not feel obliged to cooperate, although a great number of the patients are insured. Let us hope that the latest and current legislation will provide improvements for the patients concerned. Its aim is to provide an opportunity of medical treatment by the public health department and the opportunity to afterwards charge the costs of the treatment to the insurance branches of the social security system.