Sizing Europe leads the field for the Champion Chase (1730 BST) on Tuesday's first day of the Punchestown Festival.
He renews rivalry with the 2011 winner Big Zeb, but potential British runner Wishfull Thinking heads for Saturday's Celebration Chase at Sandown instead.
A six-strong field is completed by Captain Cee Bee, China Rock, Gauvain and Realt Dubh.
Cheltenham Gold Cup ante-post favourite Sir Des Champs runs in the Champion Novice Chase (1840).
Nearly 100,000 punters are expected in County Kildare over five days for Ireland's biggest annual jump meeting.
The ground at the track is verging on heavy after persistent downpours in the build-up.
Trainer Henry de Bromhead said Sizing Europe, who will be ridden by Andrew Lynch, was "bouncing" ahead of the two-mile Grade One race (1730 BST).
The 10-year-old lost his Queen Mother Champion Chase title at Cheltenham last month when beaten by Finian's Rainbow, with the pair having to bypass the last fence after an earlier fall.
"He seems in really good form. We had him out this morning and he nearly ran away with Andrew. He's bouncing," said De Bromhead on Monday.
"We've had mixed weather and the ground is softer than you might have expected for this time of year, but it was pretty soft when he won the Tied Cottage Chase here in February and also in the Tingle Creek at Sandown, so hopefully he'll be all right.
"He seems fresh and well, so fingers crossed."
Big Zeb, trained by Colm Murphy, was the narrow victor when the pair clashed in this race 12 months ago, but Sizing Europe has come out on top in their two meetings this season.
Murphy hopes the application of cheekpieces may help his horse bridge the gap.
"I'm happy with him at home. Both him and Sizing Europe are coming to the end of long seasons, so who knows what will happen?" said Murphy.
China Rock runs for Mouse Morris, dropping back over a mile in distance having travelled well before weakening into eighth in the three-and-a-quarter-mile Cheltenham Gold Cup.
Noel Meade's Realt Dubh was fifth in the Champion Chase at Cheltenham last month on what was his first run of the season.
Sir Des Champs, who is unbeaten in six runs for trainer Willie Mullins, is a hot favourite for the Champion Novice Chase after winning at the Cheltenham Festival for the second year running last month.
"I'm happy he's in good shape and I wouldn't be worried about the ground for him, he should be fine," said Mullins.
Meanwhile, ante-post favourite Quito De La Roque has been ruled out of the Punchestown Gold Cup on Wednesday with a sinus infection and Quel Esprit is the new market leader.