Leinster extended their lead at the top of the RaboDirect Pro 12 after holding off a determined Cardiff Blues side 23-19.
It was a 10th successive win for the Irishmen, but they were hanging on desperately in the closing stages and can thank their well organised defence, rather than their renowned attack, for seeing the game out.
Sean O'Brien and Rob Kearney scored tries for Leinster with Jonathan Sexton booting two conversions and two penalties. Fergus McFadden added another penalty.
Gethin Jenkins crossed for the Blues and Leigh Halfpenny added three penalties and a conversion to Dan Parks' drop-goal.