BBC world's media reporter
The doctor carrying out the surgery stresses that he is performing what he calls "gender correction" rather than sex change operations.
As a conservative Islamic state, Saudi Arabia does not allow surgery for transsexuals, but permits operations on people with an intersex condition.
Three of the five sisters have already been operated on. The remaining two are to have surgery next week.
The sisters' ages range from 19 to 38.
Dr Yasser Jamal - who is performing the operations at King Abdul Aziz University in Jeddah - says the sisters are not Saudi by origin but Arabs who have lived in the country all their lives. None of them is married.
After their operations, they are moving to a different district, although Dr Jamal says they are not facing problems in their community.
In tacit acknowledgement of the sensitivity of the subject in Saudi Arabia, Dr Jamal, himself a Saudi, emphasised that the sisters fell into the intersex category - without clear male or female sexual characteristics.
He said that he would never perform surgery on transsexuals - people with normal genitalia but who believe that they belong to the opposite sex.
He said Islam did not allow people to change what God had created.
In Saudi Arabia, transsexuals are associated with homosexuality, which is banned in the kingdom.
Dr Jamal has performed more than 200 intersex operations.
He said the transition from being treated as a woman to a man in Saudi Arabia usually went smoothly, but that there could be problems for men becoming women.
He said they found the restrictions of being female in Saudi Arabia difficult to cope with. . . .