The common health insurance system imposes a duty of insuring a number of varied entities. However, in the method of listing entities that are obliged to take out insurance some social groups were left out. This was certainly the intention o f the legislator because although the insurance is called „common”, health insurance originates mainly from workers’ insurance, addressed primarily to impecunious hired workers. With a view to encompassing more and more social groups with the benevolence of health insurance, the legislator has been expanding the list o f entities obliged to take out health insurance, granting all the others the right for voluntary insurance. This article, whose subject has not yet been dealt with in Polish litera...