PetroChina became the world's most valuable publicly traded company at the end of 2007.
PetroChina briefly held the top market-capitalization position in late 2007 after its Shanghai listing produced extraordinary demand. On its first trading day, the company was valued at more than US$1 trillion, although the share price later fell sharply.
PetroChina is the listed arm of China National Petroleum Corporation, one of China's major state-owned energy groups. Its activities include exploration, production, refining, chemicals and fuel distribution.
The 2007 valuation is often discussed as an example of how market capitalization can be affected by a relatively small freely traded share float. PetroChina's full corporate value and the value of its publicly traded shares were not identical. The company did not permanently remain the world's most valuable firm; later rankings were shaped by oil prices, Chinese equities and the growth of technology companies.