Troopers say the wreck happened off Refinery Rd. on US 81 south of Duncan just after 6 last night.
They say 53-year-old Paula White of Duncan was heading south on Highway 82 when she nodded off.
Troopers say White's car drifted into northbound traffic and she was killed when her car collided with a van.
Troopers say the driver of the van, Margaret Knox of Marlow, was pinned in her vehicle for about an hour before she was freed.
She suffered leg and internal injuries.