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Oscar Pistorius, who made history as the first amputee to participate in a track event at the Olympic Games, came last in his 400 metres semi-final on Sunday night.
He finished in 46.54 seconds which was more than a second slower than his qualifying time on Saturday.
He said, however, that he was overwhelmed by his Olympic experience and by the support he had received.
The 25-year-old will take part in the men's 4 x 400m relay heats on Thursday.
Usain Bolt decisively defended his 100-meter title last night.
He beat Jamaican training partner Yohan Blake in an Olympic record of 9.63 seconds, just .05 of a second outside his world mark.
World champion Blake equaled his personal best with 9.75 and Justin Gatlin took bronze in 9.79.
