The Italian town of L'Aquila is welcoming leaders of the G8 group of industrialised nations for its annual summit, just three months after it was hit by a strong earthquake.
Leaders from a host of other countries - including Brazil, India, China, South Africa, Mexico, Nigeria and Egypt - not to mention international organisations, such as the UN, the International Monetary Fund and the World Bank, will also be present.
Here are some of the topics they will be discussing:
The G8 leaders are expected to make their strongest statement ever on global warming. Analysts say they will agree that the world must cut greenhouse gas emissions by 50% by 2050 - with rich nations reducing them by 80%.
Greenpeace makes its point with an inflatable iceberg in Paris
In addition, they will probably say that any human-induced temperature rise should be held to 2C - a level considered to be the danger threshold.
Not all the non-G8 countries invited to the summit - have committed to carbon emission targets. Brazil has signed up to the 2C threshold, and China is committed to achieving a low-carbon economy - but only slowly, to avoid any social and economic unheaval.
India, for its part, does not want to make any firm commitments. It has millions living in poverty and believes the problem should be solved by the rich nations.
This could be one of the more animated discussions. The host country, Italy, has been criticised by aid agencies - and harshly condemned by the singer-turned activist Bob Geldof - for drastically cutting its development budget in recent months.
The biggest aid initiative of the summit is expected to be US President Barack Obama's announcement of a plan to improve food security in Africa, by putting an extra $3bn (1.8bn) to $5bn into agricultural development aid. Mr Obama has reportedly put pressure on Italy to contribute to this project.
Prime Minister Silvio Berlusconi, meanwhile, says the G8 is committed to laying the groundwork for a G8-Africa Partnership designed to improve access to to water and basic sanitation, before the end of the year.
The G8 leaders are likely to discuss:
- How to reform banks to prevent another financial crash
- How to clean up toxic assets held by financial institutions, especially in Europe and the United States
- How to strengthen the role of the new Financial Stability Board
- Reform of institutions such as the International Monetary Bank and the World Bank, to give developing countries a bigger voice
But analysts say key decisions are likely to be postponed until the next meeting of the G20 in the US city of Pittsburgh, in September.
Chinese President Hu Jintao is one of the world leaders invited to Italy
G8 summit agendas are frequently derailed by international events. Over the last few days, the violence in the Chinese province of Xinjiang has been one of the biggest stories on the world news agenda, and German Chancellor Angela Merkel has been quoted as saying she will raise the issue with the Chinese President Hu Jintao.
Some of the world's other major problems will also land on the G8's doorstep:
- Iran's disputed presidential elections and nuclear ambitions
- North Korea's nuclear programme
- The struggle against terrorism
- Afghanistan and Pakistan - the leaders are likely to support the elections in Afghanistan next month, and discuss a plan to replace poppy cultivation with legitimate farming