American tennis player Wayne Odesnik faces a possible two-year ban after pleading guilty to importing human growth hormone (HGH) into Australia.

Customs officers found eight vials, each containing 6mg of HGH, in Odesnik's baggage, when he arrived in Australia in January to play in the Brisbane International and Australian Open.

The American 24-year-old, ranked No.98 in the world, pleaded guilty in the Brisbane Magistrates Court to importing the hormone and was fined $8000 and ordered to pay $1142.80 in costs.

Odesnik made the quarter-finals in Brisbane, and reached the second round of the Australian Open, for which he picked up a $31,500 pay cheque.

The matter will now be referred to the International Tennis Federation (ITF).

Under the World Anti-Doping Authority (WADA) code - to which the ITF is a signatory - the penalty for possession of a prohibited substance is a two-year ban from the sport.

ITF head of communications Barbara Travers said it was her understanding that a two-year ban was the penalty for such an offence.

The Tennis Anti-Doping Program, which the ITF manages, would begin an investigation as soon as possible.

"Now that the civil case is concluded, the Tennis Anti-Doping Program will being an investigation, as we would in any doping case," Travers said.

"We don't really comment on it once it's gone into the system.

"We've confirmed that he's going to be investigated but other than that, we don't really comment."

Odesnik has a career-high ranking of No.77.

He has played in four tournaments in the United States since the Australian Open, advancing beyond the first round just once.

The Australian Sports Anti-Doping Authority was aware of the charges against Odesnik before he played in the season's opening grand slam.

"We've been aware of the case as part of our usual information-sharing agreement with the Australian Customs Service - that's how we got notified," an ASADA spokesman told the Associated Press.

"We had to wait for Customs to take it to court. Now that has happened, our investigation team will look at the information going forward."