While the size of your ship and the length of the cruise will determine the number and type of ports you can visit, the distance between ports is also a consideration when evaluating a South America cruise. Due to the great distances covered along the Atlantic and Pacific coasts, loop cruises that start and end at the same point are less common than one-way cruises, which begin in one port and end in another.

Typically, the shortest itineraries are those lasting a week to ten days that sail one-way from Rio de Janeiro, Brazil, to Buenos Aires, Argentina, or which make a loop from one of those embarkation ports. The number of ports of call and days at sea are determined by the length of the cruise, but you can usually count on at least one port day in Uruguay -- usually Montevideo -- and several other days ashore exploring small ports in either Brazil or Argentina. Itineraries that include an overnight port call in either Rio or Buenos Aires, or that begin the cruise with an overnight stay on board in either of those cities, offer the chance to sample the nightlife and local cuisines.

Cruises of fourteen days or longer are almost always one-way and afford the opportunity to sail from the Atlantic to the Pacific (or vice versa) around Cape Horn, the southernmost tip of South America, and through the Strait of Magellan. From Atlantic-coast embarkation ports of Rio de Janeiro and Buenos Aires -- or Valparaiso, Chile, on the Pacific coast -- you can spend two to three weeks sailing past glaciers and through rugged Chilean fjords with stops at such ports of call as Port Stanley in the Falkland Islands; Puerto Montt and Punta Arenas in Chile; Montevideo in Uruguay; and Ushuaia in Argentina. As much as half the voyage can be spent sailing between ports of call, often through scenic areas close to the coastline. Ships on repositioning cruises and world cruises often include port calls in South America on their itineraries.