The 0.3ha sanctuary near Alexandra was set up in November 2009 by the Central Otago Ecological Trust, alongside the Department of Conservation, Landcare Research and the Central Stories Museum.
Of the 16 skinks being released, nine are fully mature.
The other seven are young adults not of breeding age.
Grand and Otago Skink Recovery Programme manager Andy Hutcheon said the initial release of 12 captive-bred adults in 2009 was a test to see if the skinks could survive in the area.
"We knew, historically, those animals lived in the area, but no-one had recorded them in those particular rocks."
He said the new arrivals would probably not displace the existing skinks but, as with any animals, there would be some competition.
"In my view, if there are not enough on the rocks bumping into each other, then there are not enough in the area."
Trust chairman Grant Norbury said three of the young adults being released were bred in the wild, and he hoped they would provide genetic diversity to the population once they became mature.
Mr Norbury said Otago skinks were found nowhere else in the world outside of Otago, and were New Zealand's largest skink, growing up to 30cm long.
In February, four Otago skinks were born in the sanctuary.
Mr Norbury said he was sure two of the four survived the winter.
One of the other two was attacked by an adult skink and died, and the other was last seen being chased out of its territory by an adult.
He said because Otago skinks took four years to fully mature, increasing their numbers was very difficult.
The trust is hoping to built a new predator-proof fence and extend the size of the sanctuary to 14ha.
At a cost of $80 a metre, the new fence would cost $370 a metre less than the existing fence.
The Grand and Otago Skink Recovery Programme was established in 2002 after evidence showed both species could be extinct within 15 years.
