Tennis is looking at whether it can adopt measures pioneered by cycling to weed out drug cheats.
ITF anti-doping manager Stuart Miller said tennis' governing federation is working hard to do more blood and out-of-competition tests on players.
In the wake of cyclist Lance Armstrong's life ban from sports for doping, Roger Federer and Andy Murray have called for more out-of-competition and blood testing in tennis.
Murray called the Armstrong case "pretty shocking."
"You would hate for anything like that to happen to your own sport," Murray said before the season-ending ATP finals.
Federer said: "We don't do a lot of blood testing during the year. I'm okay having more of that."
In a phone interview, the ITF's Miller said: "We're working hard to try to increase the proportion of out-of-competition testing, and particularly blood testing, and we've been working on that for a while."
"I'm hopeful that by the end of the year we'll have made some inroads into improving that. Like any anti-doping programme, we're subject to resource constraints," he said.
Cycling, followed by track and field, also runs so-called "biological passport" programmes that monitor athletes' blood readings over time for possible tell-tale indications of doping. The federations for those sports, the UCI and the IAAF, have used evidence of doping gathered from their passport programmes to ban athletes and to target others for more testing.
Without giving a fixed timeframe, Miller said "it would be nice" if tennis can establish a similar monitoring system in 2013.
"We are looking very, very carefully at an athlete biological passport programme in tennis," he said.
"I don't want to say it's definitely happening until we actually say, 'Here's a programme. It's up and running.' We're looking at it to ensure that if we do run it, we can run it properly."
The ITF and the World Anti-Doping Agency conducted just 21 out-of-competition blood tests - used to detect the abuse of growth hormone, transfusions using blood from donors, and blood-doping substances CERA and HBOCs - in tennis in 2011.
Just three of those were on women players. ITF statistics on its web site show it didn't test Serena Williams out of competition at all in 2010 and 2011, years she won the Australian Open and Wimbledon and lost a US Open final. The ITF did test her in competition.
The US Anti-Doping Agency's web site also shows that before one test in the second quarter of this year, it hadn't organised a test on the 15-time major winner since 2008.
Williams said last month, "I get tested a lot."
"For me, it's a pretty intense system, and I know a lot of the players feel the same way," she said.
Cycling conducted 6500 more tests than tennis on professional road racers last year and an average of nine tests per rider, compared to an average 3.4 tests per player in tennis.
Of the 642 tested tennis players, 510 were not tested out of competition at all in 2011. By way of comparison, Canadian cyclist Ryder Hesjedal, winner of the Giro d'Italia, has had 22 urine tests and 13 blood controls so far this year.
The ITF budget shows it spent US$1.3 million on testing in 2011, which Miller said doesn't include salaries and other operating expenses.
That is less than Federer and Williams each pocketed for winning the men and women's singles titles at Wimbledon this year.
Cycling says it spent US$4.7 million on testing alone in 2011, with teams, riders, race organisers and the UCI all contributing.