Giffords' operation at Memorial Hermann Hospital in Houston took more than three hours Wednesday. Surgeons used a ceramic implant to replace a segment of her skull that was removed after she was shot in the head in January, the Houston Chronicle reported.
Dr. Dong Kim, who headed the neurosurgery team, said at a news conference that Giffords "looks great." She can stop wearing a protective helmet.
Giffords, D-Ariz., was wounded during a constituent event in January. Jared Loughner, the accused gunman, allegedly shot 19 people, killing six of them.
Kim said bullet fragments remain in Giffords' head in areas that would be difficult to get to. They have not caused any infection, he said.
Dr. Gerard Francisco, who heads the team caring for Giffords at TIRR Hermann Memorial, said she may be ready for more intensive rehab when she returns.