Boxer David Munyasia's appeal against his exclusion from the Olympics has been rejected, the Court of Arbitration for Sport ruled on Sunday.
Munyasia says he never took a banned substance
The 24-year-old bantamweight from Kenya was sent home last Tuesday after testing positive for cathine, which is a banned substance.
Munyasia's was the first positive case among more then 200 dope tests carried out on athletes arriving in Athens.
He has repeatedly said he is innocent of any wrongdoing.
"I am clean. I have never taken qat or any drug. I believe
there was a mistake somewhere," Munyasia said on returning to Nairobi last week.
Munyasia said he drank only coffee and an energy drink prior to being tested and took an antibiotic.
Cathine is a substance from the leaf of the qat plant, commonly chewed as a recreational drug in east