Captain Ricky Ponting top-scored with 71 as Makhaya Ntini scythed through the Australian line-up with figures of 5-64, exposing the middle-order vulnerability which South Africa had predicted before the match.

The visitors were 38 without loss in reply with AB de Villers on 14 and captain Graeme Smith on 18.

"To take five wickets against Australia is a huge achievement," said a beaming Ntini.

"It has been a good day for South Africa overall. This is one of the things that we wanted to happen.

"From a bowling point of view it's been an amazing day -- taking five for the first time I come and play at the WACA -- it's a great opportunity."

Australia coach John Buchanan admitted his side had felt under heavy pressure to perform.

"It would be nice if we could live up to everybody's expectations every time we bat and every time we bowl," he said.

"The reality is it's international sport, it's very competitive. We're just not superhuman I suppose."

He said Australia had suffered when South Africa began to tidy up their bowling after lunch.

"Up until lunch I thought from South Africa's point of view they were a little bit lacking in the disciplines of line and length and we took advantage of that," he said.

"Come the second part of the day, almost vice versa -- they tidied their discipline up and obviously we didn't.

"I think the South African bowlers probably adjusted their lengths more than anything else in the last two sessions."

Apart from Ponting's punchy innings it was a dour day for the Australians who won the toss and elected to bat on a wicket which played fairly true.

They got off to a terrible start with Matthew Hayden pulling an Ntini delivery skyward and into the hands of Jacques Rudolph before a run had been scored.

Ponting, who blasted a dozen fours in his 71, and Justin Langer gave the home side something to cheer about as they reached lunch at 96-1.

Ntini brought the partnership to an end as he dismissed Langer for 37 through another botched pull to Smith at mid-off.

Shaun Pollock then trapped Ponting lbw for 71 with a ball which nipped back from the off side.

Australia were still in command at 173-3 at tea but endured a horrendous evening session.

One-day specialist Andrew Symonds made 13, wicketkeeper Adam Gilchrist six and hometown hopeful Michael Hussey 23 as the middle order folded.

Only Brad Hodge offered serious resistance with 41 before he was caught behind by Mark Boucher off Ntini.

Andre Nel cleaned up the tail, having Nathan Bracken caught behind for 10 and Glenn McGrath for a duck.

It could have been worse for the hosts if South Africa had held a series of dropped catches. Boucher was the main culprit, missing a top edge from Hodge when he was on three.

Gilchrist was also dropped at first slip by Justin Kemp off Ntini, though he went four balls later without adding to his tally.

South Africa took the field without star all-rounder Jacques Kallis, who has an injured left elbow and failed a last-minute fitness test.

He was replaced by top-order batsman Rudolph.