Any library has the primary function to cater to the informational requirements of the patrons within minimum possible time. For this purpose, libraries acquire resources subject to financial constraints. No library can provide every document to every member out of its stock. The available stock of a library is shared by its patrons by borrowing books for a particular time and then to return in the library for others.With the passage of time and emergence of new techniques, the circulation system of library transforms accordingly. Libraries implemented the modern techniques to save the time of its patrons and to share its resources at national and international levels. The present paper is an attempt to discuss some of the important and widely used library circulation systems. 

Keywords:Financial constraints;Informational requirements;Library circulation systems.