According to study done by Poker Players Research (PPR), the US is still the top online poker market despite the UIGEA being passed in 2006. There are currently more than 10 million American real money players, which completely dwarfs the runner up, the UK, at 1.9 million.

Thanks to the fact that many of the major online poker rooms decided to abandon the US market after 2006, a few rooms like Pokerstars and Fulltilt have managed to amass more than half the online poker market share. It will be interesting to see how the market develops if and when the US open their borders to regulated online poker.

According to the study, the 5 biggest markets for online poker currently are:

USA 10 million real money players
UK 1.9 million
Germany 1.6 million
Nordic countries 1.4 million
France 1.3 million

Source: E Gaming Review