Article II, Section 3 of the U.S. Constitution grants the president authority to call both houses or either house of Congress into session in extraordinary circumstances. As of November 2013, U.S. presidents have called the Senate into special sessions 46 times -- usually to consent to appointments or ratify treaties -- and both houses of Congress into special sessions 27 times. The most recent special session of Congress was called in 1948 by President Harry S. Truman.

Amendment XX

The main reason the president rarely has to call Congress into special session has to do with changes made by the 20th Amendment, ratified in 1933. Prior to the ratification of the 20th Amendment, Congress convened in December and typically adjourned around March. Since 1933, Congress convenes on January 3 and typically does not adjourn until late in the year. The president rarely has to call Congress into session because Congress isn't generally out of session long.

Call Back Provisions

Another reason that the president rarely needs to call special sessions of Congress is that Congress began including provisions for congressional leaders to recall Congress in their adjournments. From 1973 to 1975, congressional leaders used these call-back provisions during the Watergate scandal. Most congressional adjournments since then have included such provisions, circumventing the need for the president to call a special session.