As today's information environment changes rapidly with the development of information technology, users expect a variety of the library services that meet their emerging needs. This paper reports the concept of reciprocal borrowing and analyzes the cases of reciprocal borrowing programs in the US. Particularly, this paper introduces (1) three cases of state-wide library cards such as Georgia's PINES card, Maryland's MPower card, and Michigan's Michi card. (2) Public library systems in the U.S. also are introduced as a type of reciprocal borrowing. Another type of reciprocal borrowing mentioned in this paper was (3) an mutual agreement between and among libraries. The author sought the deeper understanding of reciprocal borrowing by mapping the cases described in this paper into three models of reciprocal borrowing Kwak et al.(2010) suggested. This paper concludes with a few important considerations in implementing reciprocal borrowing services in Korea.