Serena Williams has beaten her big sister Venus 7- 7-6 to advance to the semi-final's at the US Tennis Open.
It's the first time the foruth seed has reached the last four since she won in New York six years ago.
She did it the hard way having to save 10 set points after being down 5-3 in the first tie-breaker and 5-2 in the second.
Serena says the intensity of the match made it feel like a final.
She'll play Russia's Dinara Safina in the semis.
