Private legislation in the United States is one of the most original types of legislative instruments. This institution is typical of the United States and many other countries of Anglo-Saxon origin. What decides about the special nature that type of legislation is defined in its name: it is a legislation relating to an individual person, either legal or natural. In practice, it mostly includes regulations concerning claims against the U.S. government and immigration matters. There are a lot of controversies about the use of private legislation. The breach of the separation of powers principles is the most serious objection. What is characteristic is that it covers the relations not only between the legislative and judicial branches, but also between the legislative and executive ones. Moreover, in view of some provisions of the constitution, the principle of "equal protection of law" may be challenged. Another defect can be predicted relatively easily: the promotion of strictly egotistic interests and even inducing corruption. Private bills are used to maintain links between the representative and the electorate. The existence of that kind of legislation is also justified by the rule of equity. To sum up, potential defects of private legislation do not at all relate to those matters that might be suggested by intuition. This conclusion is true for the United States now, and is likely to prove the case in Poland if private legislation would be introduced.