Drug-testers believe they could be able to snare users of human growth hormone at the 2004 Olympic Games.
The International Olympic Committee and World Anti-Doping Agency said they are making progress toward a test for HGH.
Arne Ljungqvist, the IOC medical commission chairman, said: "I'm sure we are approaching a stage where we will have something in place.
"Whether it will be fully ready in Athens or not, that is what we wish to know."
HGH works like an anabolic steroid to build muscle mass and help athletes recover faster from hard training.
Although it has been around for decades and is on the list of banned substances, it remains undetectable in standard doping controls.
Attempts to devise a test for HGH have dragged on for years, with a number of projects stalled by a lack of funding.
But the IOC and Wada staged a two-day meeting in Switzerland this week to bring together scientists involved in six different research projects.
Wada director general David Howman said: "We are optimistic that we're heading in the right direction."
If a test is finally devised, it will mark a second major success in a short period in sport's war against drugs.
Earlier this month, US anti-doping officials unveiled a new test for the previously-undetectable steroid tetrahydrogestrinone (THG).
Several athletes, including British sprinter Dwain Chambers, have tested positive for the substance.