With bright smiles and energy to spare, formerly conjoined twins Mohamed and Ahmed Ibrahim of Egypt have returned to Dallas, four years after a marathon operation to separate them.

The 6-year-old boys, who are walking on their own and speaking in English and Arabic, were separated here in October 2003. They were born joined at the tops of their heads.

After their 34-hour surgery, they stayed in Dallas for about two more years as their skulls were reconstructed. They returned to Egypt in November 2005.

"These boys to me represent the culmination of a very long journey, where they are arriving at what we all envisioned would be a possibility, but it turns out to be a reality," said Dr. Kenneth Salyer, chairman and founder of the nonprofit World Craniofacial Foundation, which brought the boys here for evaluation last week and has been directing their care.

During the two weeks they'll be in the United States, the boys will be evaluated by doctors in Dallas and also travel to Arizona to get an MRI that should tell more about how their brains are functioning, he said.

"But just from looking at these boys, I'm very pleased with how they've done," Salyer said. "They've made tremendous progress."

The boys came with their mother and 14-month-old brother while their father and two older siblings stayed in Cairo.

While in Dallas, the boys and a set of twins born joined at the head in Italy were guests of honor at a fundraiser for the foundation, which helps children with deformities of the head or face.

"We're joyous," Salyer said. "We're happy with them. They've been celebrating since they arrived back to their home away from home."