CAPE TOWN - The Stormers withstood a stoppage-time attack from the Chiefs to claim a 36-34 triumph in a Super 15 thriller at Newlands.
The Chiefs staged a multi-phase assault that took them close to Stormers' quarter when they were penalised at a ruck and fullback Joe Pietersen ended the match by booting the ball into touch.
It was the first win of the season for the South Africans and the first loss for the New Zealanders, who won the competition for the first time last season by whipping the Sharks from Durban.
The only disappointment for a home team was that scoring three tries left them one short of a bonus point while the Chiefs collected two, for scoring four tries and for losing by fewer than eight points.
Pietersen, promoted to first choice goal kicker after a series of early-season misses by new fly-half Elton Jantjies, finished with 21 points from five penalties and three conversions.
Right wing Gio Aplon crossed for two tries and scrum-half Nick Groom dotted down during the second half as the Stormers contradicted a reputation for being obsessed with defence by delivering a show of all-out attack.
The Chiefs have scored 14 tries in three outings — easily the best record among the 15 southern hemisphere championship teams — and played their part in a high-octane clash despite having two players sin binned.
Charlie Ngatai twice, fellow centre Tim Nanai-Williams and replacement back Andrew Horrell scored tries for the title-holders and fullback Gareth Anscombe contributed 14 points via four conversions and two penalties.