A serious crash blocked the M40 between Milton Common and Wheatley in both directions.
At about 10.50am there was a collision between a car and a motorcycle on the southbound carriageway between Junction 7 (Thame) and Junction 8 (Oxford).
The northbound carriageway was also blocked while emergency services waited for an air ambulance, but was reopened shortly before 1pm.
South Central Ambulance spokeswoman Michelle Archer said: "Our crews have been working to assess and treat one patient who has sustained serious injuries.
"That patient has been treated at the scene and taken to the John Radcliffe Hospital by land ambulance, accompanied by a doctor from the air ambulance crew."
Ms Archer could not say if the patient was a man or a woman, or the nature of the injuries.
The crash caused long tailbacks on the motorway.
Thames Valley Police said the carriageways were expected to be reopened about 12.20pm.
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