Connacht secured a surprise bonus-point win over Leinster in the Pro12 derby clash at the Showgrounds in Galway.
Tries from David McSharry, Fetu'u Vainikolo and Tiernan O'Halloran fired the hosts into a 22-6 half-time lead.
Leinster failed to mount a comeback and George Naoupu's try sealed the bonus point for Eric Elwood's men before Ronan Loughney added the fifth.
Connacht debutant Dan Parks pulled the strings at fly-half and scored a penalty and two conversions.
Parks, the league's record points-scorer, was a steadying presence at number 10 as Connacht faced into a buffeting wind early on.
Ian Madigan opened the scoring for Leinster five minutes in, drilling a penalty over to punish Johnny O'Connor for sloppy ruck play.
Michael Swift was inches away from marking his record 150th league appearance with a try, Tom Sexton doing well to deny the Connacht veteran as he crashed over the try-line.
From the resulting scrum, centre McSharry cut clean through to score a fine converted try to the left of the posts.
Madigan replied for the visitors courtesy of a meaty penalty kick from the left, however injuries to Gordon D'Arcy, Quinn Roux and Rob Kearney left Leinster needing to adjust.
Connacht took full advantage, relishing the ferocity of the forward exchanges and using the ball intelligently to put their backs into the space afforded to them by a lacklustre Leinster defence.
On one such occasion McSharry injected pace into a move and the supporting Robbie Henshaw sent Vainikolo breaking away on the left, with the Tongan winger stepping inside John Cooney's final challenge to score with Parks converting.
Connacht kept the pressure on and, when Brendan Macken interfered with Marmion at the base of a ruck, the Leinster centre was shown a yellow card.
The remaining 10 minutes of the first half saw Leinster leak eight more points.
O'Halloran scrambled over in the right corner from an Eoin Griffin pass, and with time up Parks landed a long-range penalty.
Joe Schmidt sent on all-Ireland international front row of Cian Healy, Sean Cronin and Mike Ross, early in the second period, as Leinster started to play with more directness.
Connacht were forced on the defensive, particularly after O'Halloran was sin-binned for not releasing a tackled player, but Leinster lacked their usual cutting edge.
After Henshaw went close with a drop goal effort, Leinster lost Auva'a to the sin-bin and Connacht seized their opportunity again, a lineout maul providing the platform for number eight Naoupu to plunge over.
That unconverted fourth try was followed by a final seven-pointer, replacement prop Loughney showing his alertness at a late line-out to touch down and replacement Miah Nikora converted to put 28 points between the sides.
Leinster even missed out on a consolation try in stoppage time as Healy had a foot in touch before he muscled his way over in the left corner.
Connacht: Henshaw, O'Halloran, Griffin, McSharry, Vainikolo, Parks, Marmion, Buckley, Flavin, White, Swift, McCarthy, McKeon, O'Connor, Naoupu.
Replacements: Fifita for McSharry (78), Nikora for Parks (78), Moore for Marmion (78), Wilkinson for Buckley (53), Harris-Wright for Flavin (57), Loughney for White (49), Gannon for McKeon (49), Faloon for O'Connor (53).
Leinster: R. Kearney, McFadden, Macken, D'Arcy, Nacewa, Madigan, Cooney, van der Merwe, T. Sexton, Hagan, Roux, Denton, Marshall, Jennings, L. Auva'a.
Replacements: Reid for D'Arcy (10), L. McGrath for Cooney (74), Healy for van der Merwe (46), Cronin for T. Sexton (46), Ross for Hagan (46), Toner for Roux (13), Murphy for Jennings (60).
Not Used: Carr.
Ref: Peter Fitzgibbon (Ireland).