After nearly five decades in power, the ailing Cuban leader Fidel Castro resigned on Tuesday. A look at why, and what's next.

CASTRO RESIGNS Longtime reign ends Articles • Cuban leader steps down • Local Cuban-American reaction subdued • Raul Castro: Fidel lite? • Castro long defied U.S. • Q&A: What's next? • Cuban exiles cautious • Text of Castro letter • Bush expresses hope Photos: • 50 years of power Timeline: • Communist revolutionary Video • Review of leader's life • Bush reaction • Excerpt of newscast • More international news

Q: Why did Fidel Castro resign?

A: Fidel, 81, has been seriously ill with a stomach ailment since July 2006, when he stunned the world by announcing he was temporarily turning over power to his brother, Raul, now 76. Since his illness, Fidel has appeared in a few video clips but has made no public appearances, and has reportedly undergone additional surgeries.

Q: Why now?

A: Most experts believe he is simply too ill to shoulder the day-to-day burdens of governing. He may also have wanted to thwart his critics, who have been hoping Cuba would fall into crisis if he were to die suddenly. "It's the perfect opportunity for him to step aside in a normal way," said Wayne Smith, a Cuba analyst at the Center for International Policy and head of the U.S. Interests Section in Havana in the early 1980s.

Q: What happens next?

A: Cuba's National Assembly meets on Sunday to choose a new Council of State, which is Cuba's governing body. Many analysts believe Raul Castro will be named president, although others speculate that Raul may share power with a younger leader.

Q: Is there a likely choice among the younger generation?

A: Much attention has been focused on Carlos Lage, 56, a medical doctor who is a Raul Castro ally and a proponent of economic reform. "I absolutely think that's the case," said Julia Sweig, a Cuba expert on the Council on Foreign Relations, during a conference call with reporters Tuesday. "There is a clear consciousness that because Raul and Fidel are only a few years apart ././. that Raul is looking for a way to showcase that the next generation in Cuba is ready. We may see Raul ././. leaving open the head of state perhaps to Lage."

Q: Is this transition of power going to bring democratic change to Cuba?

A: Many people hope so, but most experts believe the change will be gradual, not dramatic. On Tuesday, President Bush pledged to "help the people of Cuba realize the blessings of liberty. Eventually, this transition ought to lead to free and fair elections - and I mean free, and I mean fair - not these kind of staged elections that the Castro brothers try to foist off as true democracy."

Q: What's is likely to happen inside Cuba?

A: Raul Castro has frequently said his government will remain socialist, and he is backed by the powerful Cuban military, which he has led since the Cuban Revolution in the 1960s. Raul also reportedly holds the loyalty of Cuba's powerful internal secret police, who keep a tight rein on dissidents and critics. Few experts believe the transition will spark demonstrations in Cuba's streets, and Havana was calm Tuesday on the news of Fidel's retirement.

Q: What about the restrictions that limit U.S. citizens and Cuban-Americans from traveling to Cuba?

A: They are unlikely to change, for now. The Bush administration has tightened those restrictions, curtailing cultural exchanges that allowed many Americans to visit Cuba during the Clinton years in the 1990s. Bush has also cut back visits by Cuban-Americans, allowing them to visit the island only once every three years instead of annually.

Q: Will Fidel still be a power behind the scenes?

A: After nearly five decades of ruling Cuba with an iron hand, it seems unlikely that Fidel Castro will be completely silent. He apparently will continue to hold his post as first secretary of the Communist Party, and he retains the loyalty of many die-hard supporters in the top ranks of Cuba's government.

Q: Do the two brothers have differences on policy matters?

A: Many experts believe that Raul has been wanting to open the economy to some reforms, perhaps allowing Cubans to run more private businesses, but that he has been reluctant to do so while Fidel remained on the scene. How the tension between the brothers works out remains to be seen. "Obviously (Fidel) is not out of the game completely and says so," said Philip Peters, a Cuba expert at the Lexington Institute. "I think his departure will weaken the orthodox wing of the Communist Party and make it more likely they will move on economic reforms. It's clear they're moving that direction, but I wouldn't over-emphasize this. There is a consensus, though, that they need reforms."

Q: Will Fidel's exit change U.S.-Cuban relations?

A: Dramatic change seems unlikely. Raul Castro has stated that he is ready to open a dialogue with the United States, but the Bush administration has said that the four-decade-old embargo against the island will not be lifted until both Castro brothers have left the scene. State Department deputy spokesman Tom Casey on Tuesday said the United States remains ready to materially-assist a real democratic transition in Cuba. But he also called Raul "Fidel lite" and said "he is simply a continuation of the Castro regime, of the dictatorship."

Q: Is it possible the relationship will change when a new U.S. president takes office in January and that the U.S. embargo would be relaxed?

A: Experts say it is possible. But mindful of the politically powerful Cuban-American community in Florida and the importance of Florida in presidential politics, none of the candidates have yet backed proposals for dramatic changes. Yet many analysts believe a Democratic president would be more likely to do so, and big gains by the Democrats in November's elections would add pressure to do so. On Tuesday, a bi-partisan group in Congress sent a letter to Secretary of State Condoleezza Rice, saying Fidel's retirement was an opportunity the United States should not ignore. While many Cuban-American leaders continue to back a hard-line policy, saying any travel to Cuba only props up an evil regime, critics in Congress say the embargo has been a dismal failure.