South African President Jacob Zuma has described as "historic" a visit to his country by Angolan President Jose Eduardo dos Santos.
It is the Angolan leader's first state visit to South Africa during more than 30 years in office.
The two leaders signed a series of agreements to step up co-operation, including one in the energy field.
Relations between the two countries have struggled to recover from strains dating back to the apartheid era.
South Africa's white minority government backed rebels who fought Mr dos Santos during Angola's civil war, and there was no immediate diplomatic thaw when apartheid rule came to an end in 1994.
Mr Zuma travelled to Angola last year, signalling that ties were at last improving - and speaking after his meeting with Mr dos Santos in Pretoria on Tuesday, he said this latest visit would "go down in the history books as the final cementing of relations between the two countries".
Angola is Africa's second biggest producer of oil, and correspondents say South Africa sees it as an important potential supplier.
The two southern African neighbours' state energy companies have been discussing plans to construct a crude oil refinery in the Angolan coastal town of Lobito.