Benjamin's last three seasons have been plagued by injury
Team GB 400m runner Tim Benjamin has ruled himself out of the Olympics following a sinus problem.
Benjamin had sinus surgery to cap an injury-plagued pre-season, and took the decision to withdraw after consulting the UK Athletics medical team.
The Welshman, 26, was ranked fourth in the world in 2005, but foot and groin problems have since tormented him.
"This is a very sensible decision for Tim to have made," said UK Athletics performance director Dave Collins.
"He is an ambitious lad who wants to achieve at the highest level and is not happy just to settle for second best.
"The important thing now is for him to fully recuperate and get back to full health to enable him to have a good winter's training and to come back stronger for 2009.
"Our team of specialists will be working closely with Tim to help ensure he fulfils these aims."
The news will hit Team GB's 4x400m hopes as well as Benjamin's individual ambitions as the Cardiff athlete was a member of the relay team that reached the final in Athens in 2004.
Benjamin had two disrupted warm weather training camps this year in South Africa and Cyprus, where low-grade chronic sinusitis made it impossible for him to train at the levels required.
It is hoped that a period of rest from exercise will allow his body time to recover completely without the pressures of regular strenuous training sessions and competition.
Benjamin follows fellow Welshman and 4x400m contender Rhys Williams in missing out on Beijing.
The 400m hurdler pulled out of the Olympics last month with a stress fracture of the foot.