Flyhalf Demetri Catrakilis kicked all his side's points as the Stormers moved top of the South African conference with a bruising 15-13 Super Rugby victory over the Bulls at Newlands.
The Stormers moved to 30 points, one ahead of the Bulls with the third-placed Lions four points back after their tense 34-29 win over the Cheetahs earlier in the day.
A capacity 45,872 crowd was absorbed by a test-match like encounter in Cape Town in which both teams displayed heroic defence in South Africa's biggest domestic derby.
The Stormers' pack applied pressure on the visitors, particularly in the scrum, and forced the Pretoria-based Bulls into mistakes which Catrakilis punished with five penalties.
The home side led 12-3 at halftime but conceded the only try of the game a minute into the second half when scrumhalf Nic Groom lost possession of the ball on the Bulls 22.
Francois Hougaard initiated a brilliant counter-attack which was finished off by the blistering pace of his fellow winger Bjorn Basson.
The teams traded penalties after that, with Bulls flyhalf Handre Pollard booting his second to go with a conversion.
His miss, however, with a relatively easy chance 20 minutes from time proved costly for the visitors.
