Cardiff Blues 20 Ulster 17: A drop-goal in injury time by outhalf Nick Macleod kept alive Cardiff Blues' hopes of the Magners League title, while putting a sizeable dent in those of visitors Ulster.
It was a thrilling finish to a hard-fought battle which kept the 6,356 crowd gripped throughout.
The Blues, having won all 12 home games in the League this season, began with confidence and might have taken an early lead when Neil Best was penalised for a high tackle on home wing Rhys Williams, but Ben Blair missed the kick.
Ulster centre Paul Steinmetz was short from halfway, but put the visitors ahead with an easier kick after Blues skipper Xavier Rush was caught on the wrong side of a ruck.
A tap penalty by the alert Mike Phillips deep in his own half almost brought the Blues a try, but full-back Bryn Cunningham won the race to his kick ahead.
Another high tackle, this time by Andrew Trimble on Blair, earned the Irish centre a yellow card and Blair picked himself up to kick the equalising penalty.
The Blues were unable to score while Ulster were a man short, but shortly after he returned a brilliant break by Macleod split the visitors' rearguard and although Chris Czekaj was stopped 20 yards out, his strength and the assistance of team-mate Jamie Robinson drove the wing over. Blair converted.
Robinson was tackled on the line by Isaac Boss, while Rush and prop Taufaao Filise were denied as the Blues finished the half on top.
They should have extended their lead in the opening attack of the second session, but Rhys Williams dropped a try-scoring pass from lively flanker Andy Powell.
But Ulster gained 50 yards with a driving maul and repeated the ploy close to the line, creating a position from which Andrew Maxwell trotted over, only to be called back for a forward pass.
Tremendous Blues tackling, notably by Robinson and Powell, kept Ulster at bay.
But the defence eventually cracked, Rhys Williams and Bradley Davies letting number eight Roger Wilson through to the line, Steinmetz converting.
And a wayward pass by Macleod was hacked on by Steinmetz and his fellow centre, Trimble, raced under the posts for another converted try.
Blair struck the woodwork with a Blues penalty, but the home side hit back immediately when Czekaj sniped to send replacement Tom Shanklin over and Macleod converted.
Macleod missed with two attempted drop goals, but carelessness by Ulster wing Tommy Bowe allowed the Blues to stay in position for the outhalf to get a third chance, which he duly slotted over with what proved to be the last kick of a pulsating match.