The warrantless search of an automoble was permitted by the 1925 decision in Carroll v. United States. In recent years, the vehicle exception to the fourth amendment requirement of a search warrant has emerged as one of the most significant search and seizure tools available to American law enforcement officers. Probable cause must be combined with 'exigent circumstances' to justify a search, as the Supreme Court has emphasized. Police must show that emergency circumstances exist. Court decisions have upheld warrantless searches of vehicles in circumstances in which a search of a home or office would not be approved. The courts have most often cited vehicles' mobility as creating an exigency. Factors considered by the courts with respect to their effect upon a vehicle's mobility have included (1) the arrest status of the vehicle's occupants; (2) a delayed search at a different location, such as the station house; and (3) whether the vehicle is parked and unoccupied. In many cases, courts have upheld searches of vehicles whose occupants were already arrested, vehicles searched after a delay and at a different location, and vehicles which were parked and unoccupied. The Supreme Court has given several reasons to support its conclusion that a lesser expectation of privacy exists in motor vehicles than in other property. Such reasoning has also explained the Court's unwillingness to extend the warrantless search authority to other movable property, such as luggage. Nevertheless, the standards of both probable cause and emergency circumstances must be present to permit warrantless searches of vehicles. Warrantless searches are subjected to close scrutiny by the courts. Whenever it is reasonably practicable, securing a search warrant not only affords the greatest protection to the privacy of the citizen but also provides the greatest protection to the law enforcement officer. Footnotes are provided. For the first part of the article, see NCJ 80341.