The Egyptian conjoined twins separated by US surgeons in a 34-hour operation are in "good shape" after spending their first night apart, doctors said.
Relatives and friends prayed for a successful operation
Now in drug-induced comas to minimise the risk of brain damage, they were "looking in remarkable condition", said spokesman Dr Jim Thomas.
Joined at the crown of the head, two-year-old Mohamed and Ahmed Ibrahim had faced a lifetime of health problems.
Dr Thomas warned that the main post-op danger was that of infection.
But a year of careful planning for the operation at the Children's Medical Center in Dallas, Texas, appeared to have paid off.
"After coming back from the operating room last night the twins have had a remarkably stable course," said Dr Thomas.
"They have really thrown us no surprises in the process."
The operation involved teasing apart a complex network of blood vessels.
The boys now face years of reconstructive surgery on the areas where their skulls had fused together.
The US operation came as another set of conjoined twins were separated in Italy following a 12-hour operation.
The family and friends of the two-year-olds, who hail from an Egyptian village 640 kilometres (400 miles) south of the capital, Cairo, have been celebrating
after the long vigil.
"When somebody came up and said 'We have two boys', the father Ibrahim jumped to my neck and he hugged me and he fainted," said the twins' Egyptian doctor, Nasser Abdelal.
Born by Caesarean section in Qus, Egypt, 2 June 2001
Arrived in Dallas in June 2002
Tissue expanders inserted under skin in April 2003 to prepare for reconstruction
The twins are now in a critical but stable condition
Concerns include the risk of infection and how the wounds will heal
The boys' relatives and friends in their home village of al-Homr, near the city of Qus, had been praying for a successful outcome.
The family decided to go ahead with the operation, knowing there was a risk of brain damage or death to one or both the twins.
They said it was the only chance the boys had of a normal life.
The boys had had trouble closing their eyes, moving their necks and swallowing.
They could not stand on their own and would have faced progressive loss of functions had they remained as they were.
The five neurosurgeons completed the most difficult and dangerous part of the operation to separate their blood vessels physically on Sunday morning - about 26 hours after the twins entered the operating theatre.
A team of cranial and facial surgeons were then brought in to repair the damage to their skulls, using tissue from their thighs.
In all, a team of 40 doctors, nurses and other staff took part.
In Italy, doctors also successfully operated on twin girls joined at the temples, it has emerged.
The four-month-old twins, from Greece, were separated in a 12-hour operation performed by Italian doctors in a Rome hospital.
Doctors said the operation had been less complicated than that of the Egyptian boys because the girls did not share internal organs.
The girls are said to be recovering well in intensive care, although doctors told the AFP news agency that special precautions against infection would be taken for the next few days.
News of the girls' operation had been kept low profile because the parents had insisted on secrecy to protect their identities.