Australia won the toss and sent Sri Lanka in to bat in their World Twenty20 Super Eights match at Newlands.
The match is effectively a knock-out encounter. The team that wins will go through to the semi-finals, while the losers will be eliminated.
Adam Gilchrist captained the Australian team, with Ricky Ponting ruled out because of a hamstring injury suffered during his team's defeat against Pakistan in Johannesburg Tuesday.
All-rounder Shane Watson replaced Ponting. He played his first match of the tournament after recovering from a similar injury.
Sri Lanka fielded the same team that beat Bangladesh in Johannesburg Tuesday.
Australia: Adam Gilchrist (captain), Matthew Hayden, Andrew Symonds, Michael Hussey, Brad Hodge, Michael Clarke, Shane Watson, Brett Lee, Mitchell Johnson, Nathan Bracken, Stuart Clark.
Sri Lanka: Mahela Jayawardene (captain), Sanath Jayasuriya, Upul Tharanga, Kumar Sangakkara, Chamara Silva, Tillakaratne Dilshan, Jehan Mubarak, Farveez Maharoof, Chaminda Vaas, Lasith Malinga, Dilhara Fernando.
Umpires: Ian Howell (RSA), Asad Rauf (PAK).
Third umpire: Tony Hill (NZL).
Match referee: Mike Procter (RSA).