Former world championCaster Semenya is set to run her first 800-meter race of the Olympic year at a meet in northern South Africa on Saturday.
Semenya, who won silver defending her title at last year's world championships in South Korea, is listed to compete in the 800 at Potchefstroom having run just once competitively in 2012 - when she won a 400 race on March 3.
It also will be Semenya's first two-lap race under new coach and former Olympic champion Maria Mutola.
L.J. van Zyl will compete in the men's 400 hurdles, the event he won bronze in at the 2011 worlds.
The pair are South Africa's best hopes for track medals at the London Games, which will be the first Olympics for the 21-year-old Semenya if she makes the team as expected.
Semenya has had a tumultuous three years since she won the world title as a little-known teenager in Berlin in 2009. She underwent gender tests and didn't compete for 11 months.
She struggled last year with a persistent lower back injury and fell out with former coach Michael Seme just before the 2011 worlds, where she finished second to Mariya Savinova of Russia.
Sunette Viljoen, the South African who won bronze in the women's javelin at the worlds, will also compete on Saturday. Mbulaeni Mulaudzi, a former world champion and 2004 Olympic silver medallist, will run in the men's 800.
South Africa is targeting 12 medals at the London Games after only winning one silver, in the men's long jump, in Beijing four years ago. That was the country's worst Olympic performance since its return at Barcelona in 1992 following the end of apartheid.