This year's G8 has more than enough weighty issues to deal with, from reform of the global financial system to food security, climate change, and development in Africa.
Chinese President Hu Jintao was expected to attend, but returned to China abruptly to deal with violent ethnic clashes in Xinjiang Province. China is one of five developing market economies – along with Brazil, India, Mexico, and South Africa – that have attended the meeting for the past five years.
On the table for discussion will be tough new curbs on greenhouse-gas emissions. Security issues are also on the agenda, with Italian Prime Minister Silvio Berlusconi saying the summit could move to tighten sanctions against Iran. Some G8 officials, however, have said that the meeting might limit statements to a condemnation or measures such as the withdrawal of diplomats.
President Barack Obama is expected to press for further economic stimulus, something British Prime Minister Gordon Brown has indicated he supports. But other European leaders, especially German Chancellor Angela Merkel, may not be as willing to follow that lead.
Both the US and Europe are confronting devastating jobless numbers: Unemployment in the euro zone is at a 10-year high of 15 million, while that in the US rose to a 26-year high of 9.5 percent in June.
The gathering is being hosted amid the rubble and ruined buildings of L'Aquila, a medieval mountain town which was devastated by an earthquake in April that killed 300 people and left 50,000 homeless. It has since been rattled by hundreds of aftershocks.
It was Mr. Berlusconi's idea to move the G8 from its original location, a former American military base on an idyllic island off the coast of Sardinia, where a futuristic-looking conference center was being specially constructed for the meeting.
His intent was to show "solidarity" with the victims of the quake and to provide a suitably sober setting for this year's G8.
Instead of staying on luxury cruise ships and at five-star hotels, the G8 leaders will have to make do with a hastily converted police barracks on the outskirts of L'Aquila. One of the few concessions to frivolity is a basketball hoop installed outside the block reserved for President Obama.
As the summit gets under way, questions about the wisdom of meeting in the city have dogged Mr. Berlusconi, whose standing was already seriously damaged by salacious headlines about his alleged involvement in sex scandals.
Italy's president, Giorgio Napolitano, has begged politicians to call a "truce" during the three-day summit, so that mudslinging over Berlusconi's alleged improprieties does not harm the nation's image.
"The Italians are saying, for the sake of the country, can we just hold on for a week and get through this without making a mess of it," says Marco Colombo, a political analyst.
Giampiero Massolo, the Italian diplomat who did much of the preparation work for the meeting, said it would be a summit of "sobriety and solidarity."
• Material from the wires was used in this report.